ArticlePDF AvailableLiterature Review

Abstract

During pregnancy, fetal growth causes an increase in the total number of rapidly dividing cells, which leads to increased requirements for folate. Inadequate folate intake leads to a decrease in serum folate concentration, resulting in a decrease in erythrocyte folate concentration, a rise in homocysteine concentration, and megaloblastic changes in the bone marrow and other tissues with rapidly dividing cells To assess the effectiveness of oral folic acid supplementation alone or with other micronutrients versus no folic acid (placebo or same micronutrients but no folic acid) during pregnancy on haematological and biochemical parameters during pregnancy and on pregnancy outcomes. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2012) and we contacted major organisations working in micronutrient supplementation, including UNICEF Nutrition Section, World Health Organization (WHO) Maternal and Reproductive Health, WHO Nutrition Division, and National Center on Birth defects and Developmnetal Disabilities, US Centers for Disease Control and Prevention (CDC). All randomised, cluster-randomised and cross-over controlled trials evaluating supplementation of folic acid alone or with other micronutrients versus no folic acid (placebo or same micronutrients but no folic acid) in pregnancy. Two review authors independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. Thirty-one trials involving 17,771 women are included in this review. This review found that folic acid supplementation has no impact on pregnancy outcomes such as preterm birth (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.73 to 1.38; three studies, 2959 participants), and stillbirths/neonatal deaths (RR 1.33, 95% CI 0.96 to 1.85; three studies, 3110 participants). However, improvements were seen in the mean birthweight (mean difference (MD) 135.75, 95% CI 47.85 to 223.68). On the other hand, the review found no impact on improving pre-delivery anaemia (average RR 0.62, 95% CI 0.35 to 1.10; eight studies, 4149 participants; random-effects), mean pre-delivery haemoglobin level (MD -0.03, 95% CI -0.25 to 0.19; 12 studies, 1806 participants), mean pre-delivery serum folate levels (standardised mean difference (SMD) 2.03, 95% CI 0.80 to 3.27; eight studies, 1250 participants; random-effects), and mean pre-delivery red cell folate levels (SMD 1.59, 95% CI -0.07 to 3.26; four studies, 427 participants; random-effects). However, a significant reduction was seen in the incidence of megaloblastic anaemia (RR 0.21, 95% CI 0.11 to 0.38, four studies, 3839 participants). We found no conclusive evidence of benefit of folic acid supplementation during pregnancy on pregnancy outcomes.
Folic acid supplementation during pregnancy for maternal
health and pregnancy outcomes (Review)
Lassi ZS, Salam RA, Haider BA, Bhutta ZA
This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published in The Cochrane Library
2013, Issue 3
http://www.thecochranelibrary.com
Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
T A B L E O F C O N T E N T S
1HEADER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2PLAIN LANGUAGE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
14DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14AUTHORS’ CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21CHARACTERISTICS OF STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
53DATA AND ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Analysis 1.1. Comparison 1 Folic acid versus no folic acid, Outcome 1 Preterm birth. . . . . . . . . . . . 54
Analysis 1.2. Comparison 1 Folic acid versus no folic acid, Outcome 2 Stillbirths/neonatal deaths. . . . . . . . 55
Analysis 1.3. Comparison 1 Folic acid versus no folic acid, Outcome 3 Low birthweight. . . . . . . . . . . 56
Analysis 1.4. Comparison 1 Folic acid versus no folic acid, Outcome 4 Mean birthweight (g). . . . . . . . . 57
Analysis 1.5. Comparison 1 Folic acid versus no folic acid, Outcome 5 Mean birth weight (sensitivity analysis-after
removing Trigg 1976). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Analysis 1.6. Comparison 1 Folic acid versus no folic acid, Outcome 6 Pre-delivery anaemia. . . . . . . . . . 59
Analysis 1.7. Comparison 1 Folic acid versus no folic acid, Outcome 7 Mean pre-delivery haemoglobin level. . . . 60
Analysis 1.8. Comparison 1 Folic acid versus no folic acid, Outcome 8 Mean pre-delivery haemoglobin level. . . . 61
Analysis 1.9. Comparison 1 Folic acid versus no folic acid, Outcome 9 Mean pre-delivery serum folate. . . . . . 63
Analysis 1.10. Comparison 1 Folic acid versus no folic acid, Outcome 10 Mean pre-delivery serum folate. . . . . 64
Analysis 1.11. Comparison 1 Folic acid versus no folic acid, Outcome 11 Low pre-delivery serum folate. . . . . . 65
Analysis 1.12. Comparison 1 Folic acid versus no folic acid, Outcome 12 Mean red cell folate. . . . . . . . . 66
Analysis 1.13. Comparison 1 Folic acid versus no folic acid, Outcome 13 Megaloblastic anaemia. . . . . . . . 67
67ADDITIONAL TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
69HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70CONTRIBUTIONS OF AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70DECLARATIONS OF INTEREST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70SOURCES OF SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70DIFFERENCES BETWEEN PROTOCOL AND REVIEW . . . . . . . . . . . . . . . . . . . . .
70NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iFolic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
[Intervention Review]
Folic acid supplementation during pregnancy for maternal
health and pregnancy outcomes
Zohra S Lassi1, Rehana A Salam2, Batool A Haider3, Zulfiqar A Bhutta1
1Division of Women and Child Health, Aga Khan University Hospital, Karachi, Pakistan. 2Department of Paediatrics, Division of
Women and Child Health, Aga Khan University Hospital, Karachi, Pakistan. 3Departments of Epidemiology and Nutrition, Harvard
School of Public Health, Boston, MA, USA
Contact address: Zulfiqar A Bhutta, Division of Women and Child Health, Aga Khan University Hospital, Stadium Road, PO Box
3500, Karachi, 74800, Pakistan. zulfiqar.bhutta@aku.edu.
Editorial group: Cochrane Pregnancy and Childbirth Group.
Publication status and date: New, published in Issue 3, 2013.
Review content assessed as up-to-date: 2 January 2013.
Citation: Lassi ZS, Salam RA, Haider BA, Bhutta ZA. Folic acid supplementation during pregnancy for maternal health and pregnancy
outcomes. Cochrane Database of Systematic Reviews 2013, Issue 3. Art. No.: CD006896. DOI: 10.1002/14651858.CD006896.pub2.
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
A B S T R A C T
Background
During pregnancy, fetal growth causes an increase in the total number of rapidly dividing cells, which leads to increased requirements
for folate. Inadequate folate intake leads to a decrease in serum folate concentration, resulting in a decrease in erythrocyte folate
concentration, a rise in homocysteine concentration, and megaloblastic changes in the bone marrow and other tissues with rapidly
dividing cells
Objectives
To assess the effectiveness of oral folic acid supplementation alone or with other micronutrients versus no folic acid (placebo or same
micronutrients but no folic acid) during pregnancy on haematological and biochemical parameters during pregnancy and on pregnancy
outcomes.
Search methods
We searchedthe Cochrane Pregnancy and Childbirth Group’s Trials Register (31 December 2012) and we contacted major organisations
working in micronutrient supplementation, including UNICEF Nutrition Section, World Health Organization (WHO) Maternal and
Reproductive Health, WHO Nutrition Division, and National Center on Birth defects and Developmnetal Disabilities, US Centers
for Disease Control and Prevention (CDC).
Selection criteria
All randomised, cluster-randomised and cross-over controlled trials evaluating supplementation of folic acid alone or with other
micronutrients versus no folic acid (placebo or same micronutrients but no folic acid) in pregnancy.
Data collection and analysis
Two review authors independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy.
1Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Main results
Thirty-one trials involving 17,771 women are included in this review. This review found that folic acid supplementation has no impact
on pregnancy outcomes such as preterm birth (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.73 to 1.38; three studies, 2959
participants), and stillbirths/neonatal deaths (RR 1.33, 95% CI 0.96 to 1.85; three studies, 3110 participants). However,improvements
were seen in the mean birthweight (mean difference (MD) 135.75, 95% CI 47.85 to 223.68). On the other hand, the review found no
impact on improving pre-delivery anaemia (average RR 0.62, 95% CI 0.35 to 1.10; eight studies, 4149 participants; random-effects),
mean pre-delivery haemoglobin level (MD -0.03, 95% CI -0.25 to 0.19; 12 studies, 1806 participants), mean pre-delivery serum folate
levels (standardised mean difference (SMD) 2.03, 95% CI 0.80 to 3.27; eight studies, 1250 participants; random-effects), and mean pre-
delivery red cell folate levels (SMD 1.59, 95% CI -0.07 to 3.26; four studies, 427 participants; random-effects). However, a significant
reduction was seen in the incidence of megaloblastic anaemia (RR 0.21, 95% CI 0.11 to 0.38, four studies, 3839 participants).
Authors’ conclusions
We found no conclusive evidence of benefit of folic acid supplementation during pregnancy on pregnancy outcomes.
P L A I N L A N G U A G E S U M M A R Y
Folic acid supplementation in pregnancy
Folate is a naturally occurring vitamin while folic aid is the synthetic replacement of folate used in most supplements and in fortified
foods. Folate is essential as its deficiency can be caused by poor dietary intake, genetic factors or the interaction between genetic factors
and the environment. Women with sickle cell disease and those women in areas where malaria is endemic have a greater need for folate
and in these areas anaemia can be a major health problem during pregnancy. Women need more folate in pregnancy to meet their
need for extra blood and to meet the growing baby’s need for blood. Without adequate folate intake in a mother’s diet, she can become
anaemic and this can contribute to her baby being small, anaemic and born too early (preterm birth). Folic acid supplementation
taken before conception can reduce the chance of the baby having neural tube defects. This review looked to see if taking folic acid
supplements during pregnancy could reduce the chance of the baby being born too early and of low birthweight and to see its impact
on the mother’s blood (hematological values), folate levels and on pregnancy complications.
The review authors found 31 trials (involving 17,771 women) that looked at the impact of providing folic acid supplementation
during pregnancy. The data showed that taking folate during pregnancy was not associated with reducing the chance of preterm births,
stillbirths, neonatal deaths, low birthweight babies, pre-delivery anaemia in the mother or low pre-delivery red cell folate, although
pre-delivery serum levels were improved. The review also did not show any impact of folate supplementation on improving mean
birthweight and the mother’s mean haemoglobin levels during pregnancy compared with taking a placebo. However, the review showed
some benefit in indicators of folate status in the mother. The evidence provided so far from these trials did not find conclusive results
for any overall benefit of folic acid supplementation during pregnancy.
Most of the studies were conducted over 30 to 45 years ago.
B A C K G R O U N D
Description of the intervention
Folate is a generic term for both the endogenous form of the vita-
min occurring naturally in food and the synthetic form found in
supplements and fortified foods (Bailey 1995). It should be noted,
however, that folate is a naturally occurring vitamin while folic aid
is the synthetic replacement of folate used in most supplements
and in fortified foods. Humans are fully dependent on dietary
sources or dietary supplements and microorganisms in their in-
testinal tract for their folate supply. Folate derivatives are essential
for the synthesis of nucleic acid, amino acids, cell division, tissue
growth, and DNA methylation (Krishnaswamy 2001;Morrison
1998;Scholl 2000).
Inadequate folate intake leads to a decrease in ser um folate concen-
2Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
tration, resulting in a decrease in er ythrocyte (red blood cell) folate
concentration, a rise in homocysteine (Hcy) concentration, and
megaloblastic changes in the bone marrow and other tissues with
rapidly dividing cells (Dietary Ref 1998;Willoughby 1968). Dur-
ing pregnancy, fetal growth causes an increase in the total number
of rapidly dividing cells, which leads to increased requirements for
folate (Bailey 1995). With inadequate folic acid intake, concentra-
tions of folate in maternal serum, plasma, and red blood cells de-
crease from the fifth month of pregnancy onwards (Açkurt 1995;
Bates 1986). If inadequate folate intake is sustained during preg-
nancy, megaloblastic anaemia (a blood disorder characterised by
anaemia, with red blood cells that are larger than normal and cell
contents that are not completely developed) occurs (Willoughby
1968). Folate concentrations continueto decrease for several weeks
after pregnancy (Bruinse 1995;Smith 1983), and by the second to
third month postpartum, a third of all mothers can have subnor-
mal concentrations of folate in serum and red blood cells (Açkurt
1995). Possible causes for the decline in blood folate during preg-
nancy include increased folate demand for growth of the fetus due
to an increase in the number of r apidly dividing cel ls (Bailey 1995)
and growth of uteroplacental organs, decreased folate absorption,
low folate intake, hormonal influence on folate metabolism as a
physiologic response to pregnancy (Chanarin 1969), and dilution
of folate due to blood volume expansion (Bruinse 1995). Folate
demands may be further increased in women with sickle cell dis-
ease and women living in areas where malaria is endemic (Lawson
1988); in these areas, anaemia in pregnancy is a major health
problem. Increased folate catabolism and urinary folate excretion
(Fleming 1972;Landon 1971) may also contribute to increased
folate needs in pregnancy (Caudill 1998;Gregory 2001b;Higgins
2000;McPartlin 1993), but the findings are controversial. As a
consequence of folate deficiency, Hcy accumulates in the serum
and is found to be associated with an increased risk in cardiovas-
cular disease (Refsum 2008), late pregnancy complications such as
pre-eclampsia (Makedos 2007;Patrick 2004;Tamura 2006), and
neural tube defects around the time of conception (De Benoist
2008).
The recommended folate intake for pregnant women is 400 µg/
day (Food and Nutrition Board 1970). It was revised in 1999 after
evaluating its bioavailability from food and synthetic folate, and
the recommendation was increased to 450 µg (600 DFEs/day (di-
etary folate equivalent)) (Institute of Medicine 2000). It should
be noted that as per NICE guidelines, this amount of folic acid
when supplemented to pregnant women (and those intending to
become pregnant), before conception and throughout the first 12
weeks, reduces the risk of having a baby with a neural tube defect
(NICE 2008). However, the Food and Nutrition Board of the In-
stitute of Medicine have suggested that an increased folate intake
might delay the diagnosis of vitamin B-12 deficiency by correct-
ing the anaemia, or even exacerbate its neurologic and neuropsy-
chiatric effects (Food and Nutrition Board 1998;Herbert 1997;
Rush 1994). Further research is still needed in this area.
How the intervention might work
The relationship between pregnancy outcome and maternal blood
folate concentrations, folate intake and hyperhomocysteinaemia
cannot be ignored (Smits 2001). Plasma total homocysteine (tHcy)
is regulated by folate status (Selhub 1993), and hyperhomocys-
teinaemia is linked to vaso-occlusive disease (Green 1995). Im-
paired placental perfusion due to hyperhomocysteinaemia is impli-
cated in having a negative effect on pregnancy outcome, as are in-
adequate folate intake and low serum folate concentrations (Scholl
2000). Folate has long been used as a supplement in combination
with iron during pregnancy, largely on the basis of haematolog-
ical benefits (Fleming 1968), although deficiency has also been
associated with pregnancy complications and congenital malfor-
mations (Scholl 2000). Periconceptional supplementation with
folic acid, three months before and early in pregnancy is recom-
mended (Czeizel 1992;MRC 1991), and has been shown to reduce
the risk of neural tube defects by almost three-quarters (De-Regil
2010). Although still unproven, folic acid supplementation has
also been suggested to help prevent other fetal malformations such
as congenital heart defects (Botto 1996;Czeizel 1993;Czeizel
1996;Shaw 1995), urinary tract anomalies (Li 1995), limb de-
fects (Czeizel 1993), oro-facial clefts (Czeizel 1993;Li 1995;Shaw
1995), and pyloric stenosis (Shaw 1995).
Why it is important to do this review
The role of folate deficiency in increasing the risk of spontaneous
abortion and birth outcomes such as low birthweight, preterm
birth, and perinatal mortality is unclear (Bukowski 2009;Scholl
2000). Hence, the aim of this review is to assess the effect of folic
acid supplementation alone in pregnant women onh aematological
and biochemical parameters, adverse events during pregnancy, and
on pregnancy outcomes. We did not assess periconceptional folic
acid supplementation, or supplementation of folic acid along with
iron during pregnancy and with other micronutrients, as these
have been addressed by other reviews (Haider 2006;De-Regil
2010;Pena-Rosas 2006).
O B J E C T I V E S
To assess the effectiveness of oral folic acid supplementation alone
or with other micronutrients versus no folic acid (placebo or same
micronutrients but no folic acid) during pregnancy on haema-
tological and biochemical parameters during pregnancy and on
pregnancy outcomes.
M E T H O D S
3Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Criteria for considering studies for this review
Types of studies
We included randomised or quasi-randomised controlled trials
of folic acid supplementation alone or with other micronutrients
versus no folic acid (placebo or same micronutrients but no folic
acid).
Types of participants
We included pregnant women of any age and parity.
Types of interventions
1. Folic acid alone versus no treatment/placebo (no folic acid)
2. Folic acid+ iron versus iron (no folic acid)
3. Folic acid + other vitamins and minerals versus other
vitamins and minerals (but no folic acid)
We excluded studies that supplemented folic acid in the form of
fortification or home fortification alone or in combination with
other micronutrients. We also excluded studies in which women
were supplemented during periconception.
Types of outcome measures
Primary outcomes
Maternal outcomes
Pre-delivery anaemia (less than 10 g/dL haemoglobin or
haematocrit below 30%
Mean pre-delivery haemoglobin level
Low pre-delivery serum folate (less than 3 mg/L or 7 nmol/
L or 3 ng/mL)
Mean pre-delivery serum folate level
Low pre-delivery red cell folate (less than 100 mg/L or 300
nmol/L or 140 ng/mL)
Mean pre-delivery red cell folate
Pregnancy outcome
Preterm birth (delivery before 37 weeks of gestation)
Infant outcome
Low birthweight (birthweight less than 2500 g)
Secondary outcomes
Miscarriage (loss of pregnancy before 22 weeks of gestation)
Perinatal mortality - includes stillbirth (deaths after 22
weeks of gestation) and mortality in the first seven days of life
Pre-eclampsia- defined as blood pressure of > 140 mmHg
systolic or > 90 mmHg diastolic after 20 weeks of gestation, and
proteinuria of more than 0.3 g in 24 hours
Respiratory disease in child
Allergic disease in child
Megaloblastic anaemia
Hyperhomocysteinaemia (more than 16 micromol/L)
Search methods for identification of studies
Electronic searches
We contacted the Trials Search Co-ordinator to search the
Cochrane Pregnancy and Childbirth Group’s Trials Register (31
December 2012)
The Cochrane Pregnancy and Childbirth Group’s Trials Register
is maintained by the Trials Search Co-ordinator and contains trials
identified from:
1. monthly searches of the Cochrane Central Register of
Controlled Trials (CENTRAL);
2. weekly searches of MEDLINE;
3. weekly searches of EMBASE;
4. handsearches of 30 journals and the proceedings of major
conferences;
5. weekly current awareness alerts for a further 44 journals
plus monthly BioMed Central email alerts.
Details of the search strategies for CENTRAL, MEDLINE and
EMBASE, the list of handsearched journals and conference pro-
ceedings, and the list of journals reviewed via the current aware-
ness service can be found in the ‘Specialized Register’ section
within the editorial information about the Cochrane Pregnancy
and Childbirth Group.
Trials identified through the searching activities described above
are each assigned to a review topic (or topics). The Trials Search
Co-ordinator searches the register for each review using the topic
list rather than keywords.
Searching other resources
For identification of ongoing or unpublished studies, we contacted
major organisations working in micronutrient supplementation,
including UNICEF Nutrition Section, World Health Organiza-
tion (WHO) Maternal and Reproductive Health, WHO Nutri-
tion Division, and National Center on Birth defects and Devel-
opmnetal Disabilities, US Centers for Disease Control and Pre-
vention (CDC).
We did not apply any language restrictions.
4Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Data collection and analysis
Selection of studies
Two review authors, Zohra Lassi (ZSL) and Rehana Salam (RAS),
independently assessed for inclusion all the potential studies we
identified as a result of the search strategy. We resolved any dis-
agreement through discussion and, if required, we consulted the
third review author, Zulfiqar Bhutta (ZAB)
Data extraction and management
We designed a f orm to extract data. For eligible studies, two review
authors (RAS and ZL) extracted the data using the agreed form.
We resolved discrepancies through discussion and, if required, we
consulted the third review author. Data were entered into Review-
Manager software (RevMan 2011) and checked for accuracy.
When information regarding any of the above was unclear, we
attempted to contact authors of the original reports to provide
further details.
Assessment of risk of bias in included studies
Two review authors (ZSL and RAS) independently assessed risk
of bias for each study using the criteria outlined in the Cochrane
Handbook for Systematic Reviews of Interventions (Higgins 2011).
Any disagreement was resolved by discussion or by involving a
third assessor (ZAB).
(1) Random sequence generation (checking for possible
selection bias)
We described for each included study the method used to generate
the allocation sequence in sufficient detail to allow an assessment of
whether it produced comparable groups. We assessed the method
as:
low risk of bias (any truly random process, e.g. random
number table; computer random number generator);
high risk of bias (any non-random process, e.g. odd or even
date of birth; hospital or clinic record number);
unclear risk of bias.
(2) Allocation concealment (checking for possible selection
bias)
We described for each included study the method used to conceal
the allocation sequence in sufficient detail and determine whether
intervention allocation could have been foreseen in advance of, or
during recruitment, or changed after assignment.
We assessed the methods as:
low risk of bias (e.g. telephone or central randomisation;
consecutively numbered sealed opaque envelopes);
high risk of bias (open random allocation; unsealed or non-
opaque envelopes, alternation; date of birth);
unclear risk of bias.
(3.1) Blinding (checking for possible performance bias)
We described for each included study the methods used, if any, to
blind study participants and personnel from knowledge of which
intervention a participant received. We considered that studies
were at low risk of bias if they were blinded, or if we judged that
the lack of blinding would be unlikely to affect results. We assessed
blinding separately for different outcomes or classes of outcomes.
We assessed the methods as:
low, high or unclear risk of bias for participants;
low, high or unclear risk of bias for personnel.
(4) Incomplete outcome data (checking for possible attrition
bias through withdrawals, dropouts, protocol deviations)
We described for each included study, and for each outcome or
class of outcomes, the completeness of data including attrition
and exclusions from the analysis. We stated whether attrition and
exclusions were reported, the numbers included in the analysis at
each stage (compared with the total randomised participants), rea-
sons for attrition or exclusion where reported, and whether miss-
ing data were balanced across groups or were related to outcomes.
Where sufficient information was reported, or could be supplied
by the trial authors, we re-included missing data in the analyses
which we undertook. We assessed methods as:
low risk of bias (e.g. no missing outcome data; missing
outcome data balanced across groups);
high risk of bias (e.g. numbers or reasons for missing data
imbalanced across groups; ‘as treated’ analysis done with
substantial departure of intervention received from that assigned
at randomisation);
unclear risk of bias.
(5) Selective reporting bias
We described for each included study how we investigated the
possibility of selective outcome reporting bias and what we found.
We assessed the methods as:
low risk of bias (where it was clear that all of the study’s pre-
specified outcomes and all expected outcomes of interest to the
review have been reported);
high risk of bias (where not all the study’s pre-specified
outcomes have been reported; one or more reported primary
outcomes were not pre-specified; outcomes of interest were
reported incompletely and so could not be used; study failed to
include results of a key outcome that would have been expected
to have been reported);
unclear risk of bias.
5Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
(6) Other bias (checking for bias due to problems not
covered by (1) to (5) above)
We described for each included study any important concerns we
had about other possible sources of bias.
We assessed whether each study was free of other problems that
could put it at risk of bias:
low risk of other bias;
high risk of other bias;
unclear whether there is risk of other bias.
(7) Overall risk of bias
We made explicit judgements about whether studies were at high
risk of bias, according to the criteria given in the Handbook (
Higgins 2011). With reference to (1) to (6) above, we assessed
the likely magnitude and direction of the bias and whether we
considered it was likely to impact on the findings.
Measures of treatment effect
Dichotomous data
For dichotomous data, we presented results as summary risk ratio
with 95% confidence intervals.
Continuous data
For continuous data, we used the mean difference if outcomes
were measured in the same way between trials. We used the stan-
dardised mean difference to combine trials that measured the same
outcome, but used different methods.
Unit of analysis issues
Cluster-randomised trials
We included cluster-randomised/quasi-randomised trials in the
analyses along with individually-randomised trials. We incorpo-
rated the data of cluster-randomised/quasi-randomised trials us-
ing generic inverse variance method in which logarithms of risk
ratio estimates were used along with the standard error of the log-
arithms of risk ratio estimates.
Cross-over trials
We also looked for any cross-over trials on this topic, and such
trials were deemed eligible for inclusion, However, we did not find
any eligible cross-over trials.
Dealing with missing data
We noted levels of attrition for included studies. We also planned
to explore the impact of including studies with high levelsof miss-
ing data in the overall assessment of treatment effect by using sen-
sitivity analysis. For all outcomes, we carried out analyses, as far
as possible, on an intention-to-treat basis, i.e. we attempted to
include all participants randomised to each group in the analyses,
and all participants were analysed in the group to which they were
allocated, regardless of whether or not they received the allocated
intervention. The denominator for each outcome in each trial was
the number randomised minus any participants whose outcomes
were known to be missing.
Assessment of heterogeneity
We assessed statistical heterogeneity in each meta-analysis using
the T², I² and Chi² statistics. We regarded heterogeneity as sub-
stantial if the I² was greater than 30% and either T² was greater
than zero, or there was a low P value (less than 0.10) in the Chi²
test for heterogeneity.
Assessment of reporting biases
If there were 10 or more studies in the meta-analysis, we inves-
tigated reporting biases (such as publication bias) using funnel
plots. We assessed funnel plot asymmetry visually, If asymmetry
was suggested by a visual assessment, we performed exploratory
analyses to investigate it.
Mostly studies were old and we suspected reporting bias, therefore,
we attempted to contact study authors, where possible, asking
them to provide missing outcome data.
Data synthesis
We carried out statistical analysis using the Review Manager soft-
ware (RevMan 2011). We used fixed-effect Mantel-Hanzel meta-
analysis for combining data where it was reasonable to assume that
studies were estimating the same underlying treatment effect: i.e.
trials were examining the same intervention, and the trials’ popu-
lations and methods were judged to be sufficiently similar. If there
was clinical heterogeneity sufficient to expect that the underlying
treatment effects differed between trials, or if substantial statistical
heterogeneity was detected, we used random-effects meta-analysis
to produce an overall summary if an average treatment effect across
trials was considered clinically meaningful. The random-effects
summary was treated as the average range of possible treatment
effects and we discussed the clinical implications of treatment ef-
fects differing between trials. If the average treatment effect was
not clinically meaningful, we did not combine trials.
If we used random-effects analyses, the results were presented as
the average treatment effect with 95% confidence intervals, and
the estimates of T² and I².
6Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Subgroup analysis and investigation of heterogeneity
We planned to carry out subgroup analyses based on following
factors.
• Different doses of folate used (< 400 µg and > 400 µg)
• Different durations of folate supplementation
• Haemoglobin level of participants
• Co-interventions
Not all included studies mentioned the baseline haemoglobin lev-
els of participants and since duration and start of folic acid supple-
mentation in women during pregnancy varied, we, therefore, did
not carry out these subgroup analyses. However, subgroup anal-
yses were carried out on studies in which iron was additionally
provided with folic acid. We also performed subgroup analyses on
the dosage of folic acid.
We also reported the outcomes based on how the outcome was
defined in the individual study.
We assessed subgroup differences by the interaction tests available
within RevMan (RevMan 2011). We reported the results of sub-
group analyses quoting the χ² statistic and the P value, and the
interaction test I² value.
Sensitivity analysis
We did not perform sensitivity analyses as studies were old and of
mediocre quality.
R E S U L T S
Description of studies
See: Characteristics of included studies;Characteristics of excluded
studies;Characteristics of ongoing studies.
Results of the search
A total of 94 trial reports were considered for inclusion into this
review, finally 31 studies involving 17,771 women were included
in this review (Figure 1).
7Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Figure 1. Study flow diagram.
8Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Included studies
Thirty-one studies have been included in this review. The ma-
jority of these studies were quite old and were conducted dur-
ing the 1960s (Castren 1968;Chanarin 1965;Chanarin 1968;
Chisholm 1966;Dawson 1962;Edelstein 1968;Fleming 1968;
Hibbard 1969a;Menon 1962;Metz 1965;Willoughby 1967);
the 1970s (Balmelli 1974;Batu 1976;Baumslag 1970;Fletcher
1971;Giles 1971;Iyengar 1975;Rae 1970;Rolschau 1979;Trigg
1976;Weil 1977), and the 1980s (Blot 1981;Harrison 1985;Lira
1989;Roth 1980;Srisupandit 1983;Tchernia 1982;Pack 1980).
Three studies were published in 2005 (Charles 2005;Christian
2003;Decsi 2005), however, Charles 2005 re-analysed data that
were collected in 1966. Seven studies (Chanarin 1965;Christian
2003;Dawson 1962;Decsi 2005;Hibbard 1969a;Metz 1965;
Pack 1980) were were not included in the meta-analyses because
they either did not mention their standard deviations/standard
errors; or they reported the rise or fall in the haematological and
biochemical levels.
Most of the outcomes were defined in the same way across dif-
ferent trials except for preterm birth, pre-delivery anaemia, and
low birthweight which were defined differently, however, we still
included them and they were presented in subgroup according to
their defined cut-offs (Refer to Table 1). The majority of the stud-
ies were conducted in Europe (Balmelli 1974;Blot 1981;Castren
1968;Chanarin 1965;Chanarin 1968;Charles 2005;Chisholm
1966;Dawson 1962;Decsi 2005;Fletcher 1971;Hibbard 1969a;
Rae 1970;Rolschau 1979;Tchernia 1982;Trigg 1976;Weil
1977;Willoughby 1967), Africa (Baumslag 1970;Edelstein 1968;
Fleming 1968;Harrison 1985;Metz 1965) and Asia (Batu 1976;
Christian 2003;Iyengar 1975;Menon 1962;Srisupandit 1983).
One study was conducted in South America (Lira 1989), one in
Australia (Giles 1971) and one in New Zealand (Pack 1980). One
study (Roth 1980) did not mention the setting. The time for ini-
tiation of supplementation varied from 8th week of pregnancy till
three days postpartum. Most of the studies supplemented women
with folic acid in combination with iron (Balmelli 1974;Batu
1976;Baumslag 1970;Blot 1981;Castren 1968;Chanarin 1965;
Chanarin 1968;Chisholm 1966;Christian 2003;Edelstein 1968;
Fletcher 1971;Giles 1971;Harrison 1985;Iyengar 1975;Lira
1989;Menon 1962;Metz 1965;Rae 1970;Rolschau 1979;Roth
1980;Srisupandit 1983;Tchernia 1982;Trigg 1976;Weil 1977;
Willoughby 1967) however, only a few compared folic acid alone
with placebo (Charles 2005;Chisholm 1966;Decsi 2005;Fleming
1968;Pack 1980).
Please refer to the Characteristics of included studies table for more
details.
Excluded studies
A total of 25 studies were excluded from the review as they did not
satisfy the inclusion criteria. Hamilton 1973 was not a randomised
controlled trial. There were four studies in which folic acid was
given in combination with other micronutrients compared with a
no supplement group (Bjerre 1967;Ma 2008;Wang 2012;Zeng
2008). Similarly, Giles 1960 compared the intervention group
with historical controls; Gregory 2001 compared pregnant women
with non pregnant women; Khanna 1977 evaluated the therapeu-
tic use of folic acid in women with anaemia; and there were a few
studies in which the association of folic acid supplementation was
observed, with breast cancer, fetal apoptosis (Klinger 2006), con-
genital anomalies (Ulrich 1999) and with malaria when given with
sulphadoxine pyrimethamine (Ouma 2006). We excluded studies
in which therapy of iron and folic acid was compared with no
therapy at all (Taylor 1979;Taylor 1981). We also excluded stud-
ies in which folic acid was given in a fortification form (Colman
1974;Colman 1975). We excluded studies that compared the du-
ration of folic acid supplements (Ellison 2004;Polatti 1992), and
different dosage of folic acid supplements (Hekmatdoost 2011;
Hibbard 1969;Manizheh 2009). Trials were also excluded that
were in the form of published abstracts only and had insufficient
information to extract (Hague 1998;Kristoffersen 1979;Melli
2008;Thomson 1982). Also, one study in which results from three
trials were re analysed was excluded (Tchernia 1982a).
Please refer to Characteristics of excluded studies table for more
details.
Risk of bias in included studies
Most of the studies were conducted over 30 to 45 years ago, and we
found poor subjective and objective compliance with random al-
location, adequate concealment and blinding. Bias and confound-
ing thus seem to us the likely explanation for our findings.
Figure 2 and Figure 3 provide a graphical summary of the results
of risk of bias for the included studies.
9Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Figure 2. Methodological quality graph: review authors’ judgements about each methodological quality
item presented as percentages across all included studies.
10Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Figure 3. Methodological quality summary: review authors’ judgements about each methodological quality
item for each included study.
11Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Allocation
Sequence generation and adequate allocation concealment was a
problem in almost all the studies and control of selection bias at en-
try was often difficult to assess as many authors stated that women
were ’randomly allocated’ without actually describing the tech-
nique, still there were studies that managed to report the methods
of allocation concealment adequately (Blot 1981;Edelstein 1968;
Fleming 1968;Giles 1971;Rolschau 1979).
Blinding
Blinding was the another issue which was rarely discussed in depth,
and only few reported them adequately including Blot 1981;
Edelstein 1968;Fleming 1968;Giles 1971;Harrison 1985;Weil
1977.
Incomplete outcome data
Mostly studies provided insufficient information regarding attri-
tion rates, which meant we were unable to make any judgment.
There were only a few studies that discussed their exclusion and at-
trition rates and reported their reasons. (Balmelli 1974;Batu 1976;
Blot 1981 Castren 1968;Fleming 1968;Giles 1971 Harrison
1985;Iyengar 1975;Srisupandit 1983;Tchernia 1982).
Selective reporting
Again, studies provided insufficient information, which limited us
from making any judgment (Balmelli 1974;Blot 1981;Castren
1968;Harrison 1985;Iyengar 1975;Srisupandit 1983).
Other potential sources of bias
No other bias was identified but we had insufficient information
available to fully assess this ’Risk of bias’ domain. Consequently,
we assessed all included studies as being at ’unclear’ risk of other
bias.
Effects of interventions
a. Clinical measures of untoward events during
pregnancy and of pregnancy outcome
Preterm birth
None of the included studies reported preterm birth in accordance
with our definition of the outcome. We found two studies, of
which one defined it as birth of a baby between 36 to 38 weeks,
and another defined it as birth before 38 weeks of pregnancy. We
pooled them both to look for an association with folic acid supple-
mentation in pregnancy. Our analysis showed that administration
of folic acid supplementation during pregnancy has no impact on
reducing preterm birth (risk ratio (RR) 1.01, 95% confidence in-
terval (CI) 0.73 to 1.38; three studies, 2959 participants (Analysis
1.1)).
Stillbirths/neonatal deaths
None of the included studies reported perinatal mortality. How-
ever, three studies reported stillbirth and neonatal mortality as
a composite outcome, hence we pooled them to obtain data for
perinatal mortality. Folic acid supplementation during pregnancy
did not show any impact on reducing stillbirths/neonatal deaths
(RR 1.33, 95% CI 0.96 to 1.85; three studies, 3110 participants
(Analysis 1.2)).
Birthweight
Folic acid supplementation during pregnancy did not show any
impact on reducing low birthweight (less than 2500 g) (RR 0.83,
95% CI 0.66 to 1.04; four studies, 3113 participants (Analysis
1.3)).
We also attempted to look at the impact of folic acid supplementa-
tion during pregnancy on mean birthweight (g) of newborns and
found no association (mean difference (MD) 104.96 g, 95% CI
-0.25.50 g to 235.41 g; five studies, 774 participants; random-
effects, T² = 21694.29, I² = 90% (Analysis 1.4)). All the studies
pooled for this outcome compared folic acid + iron versus iron
alone.
The standard errors for Trigg 1976 were very small as compared
to the other trials for being plausible, therefore, we conducted a
sensitivity analysis after removing this study. Heterogeneity was
reduced from 90% to 50% (MD 135.76, 95% CI 47.85 to 223.68;
four studies, 625 participants; random-effects, T² = 4841.10, I² =
50% (Analysis 1.5)
Outcomes not reported in the included studies
The included studies did not report on the impact of folic acid
supplementation on miscarriage, pre-eclampsia, respiratory dis-
ease or allergic disease in children.
b. Haematological and biochemical parameters
Pre-delivery anaemia
12Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
The included studies used different definitions of anaemia. Eight
studies reported pre-delivery anaemia as an outcome, but only two
studies used our definition of anaemia. We included all studies
reporting anaemia but pooled them separately according to the
definition of anaemia used. Folic acid supplementation did not
show any impact on reducing pre-delivery anaemia (any cut-off
point) (average RR 0.62, 95% CI 0.35 to 1.10; eight studies, 4149
participants; random-effects, T² = 0.51, I² = 90% (Analysis 1.6)).
When studies were separately pooled according to the definition
described in the earlier section of this review, we found that sup-
plementation had no impact on reducing anaemia (haemoglobin
less than 10 g/dL) (average RR 0.35, 95% CI 0.05 to 2.42; two
studies, 2448 participants; random-effects, T² = 1.86, I² = 97%
(Analysis 1.6)).
We also looked at the impact of folic acid supplementation in
pregnancy on mean pre-delivery haemoglobin level, and found no
difference in the mean haemoglobin concentration among those
in the intervention arm compared with those in the placebo arm
(MD -0.03, 95% CI -0.25 to 0.19; 12 studies, 1806 participants;
random-effects, T² = 0.12, I² = 95% (Analysis 1.7)). All the studies
pooled for this outcome compared folic acid + iron versus iron
alone.
With regard to subgroup analysis based on dosage of folic acid
supplementation, we found no differences on improving haemo-
globin concentrations and the interaction test was insignificant
(Chi² = 1.18, df = 1 (P = 0.28), I² = 15.1%). Analysis 1.8
We also ran a funnel plot to assess the publication bias and we
found studies were equally distributed on each side except for two
outliers Figure 4.
Figure 4. Funnel plot of comparison: 1 Folic acid versus no folic acid, outcome: 1.7 Mean pre-delivery
haemoglobin level.
Pre-delivery serum folate
Folic acid supplementationin pregnancy showed a reduction in the
incidence of low pre-delivery serum folate by 62% (RR 0.38, 95%
CI 0.25 to 0.59; two studies, 696 participants (Analysis 1.11)).
We found non-significantly higher mean pre-delivery serum folate
levels among those in the folic acid supplementation arm com-
pared with those in the placebo arm (standardised mean difference
13Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
(SMD) 2.03, 95% CI 0.80 to 3.27; eight studies, 1250 partici-
pants; random-effects, T² = 2.96, I² = 98% (Analysis 1.9)). All the
studies pooled for this outcome compared folic acid + iron versus
iron alone.
For subgroup analysis based on dosage of folic acid supplemen-
tation, we found significant improvements in mean serum folate
concentration when the dose was less than 400 µg (SMD 3.70,
95% CI: 0.28 to 7.11, four studies n = 253, random effects, I² =
99%), however, no impact was seen of folic acid > 400 µg (SMD
0.68, 95% CI: -0.75 to 2.10, four studies n = 997, random ef-
fects, I² = 98%) Analysis 1.10. The interaction test for the overall
estimate was not significant (Chi² P value = 0.11, I² = 61%) sug-
gesting no difference between groups.
Pre-delivery red cell folate
None of the included studies reported data for pre-delivery red
cell folate deficiency status. However, mean red cell folate levels
were reported in four studies. Folic acid supplementation during
pregnancy did not show any impact on reducingme anpre-deliver y
red cell folate levels (SMD 1.59, 95% CI -0.07 to 3.26; four
studies, 427 participants; random-effects, T² = 2.79, I² = 97%
(Analysis 1.12)). All the studies pooled for this outcome compared
folic acid + iron versus iron alone.
Megaloblastic anaemia
Folic acid supplementation during pregnancy significantly re-
duced the incidence of megaloblastic anaemia by 79% (RR 0.21,
95% CI 0.11 to 0.38; four studies, 3839 women (Analysis 1.13)).
Outcomes not reported in the included studies
The included studies did not report on the impact of folic acid
supplementation on hyperhomocysteinaemia, respiratory disease
and allergic disease in the child.
D I S C U S S I O N
Summary of main results
From our meta-analysis of randomised controlled trials on folic
acid supplementation, we found no evidence of an effect of sup-
plements on preterm birth, stillbirth/neonatal death, mean birth-
weight/low birthweight, low pre-delivery haemoglobin and serum
red cell folate. However, we found a risk reduction on low pre-
delivery serum folate and megaloblastic anaemia.
Quality of the evidence
First, all the included studies were conducted over 30 to 45 years
ago, and we found poor subjective and objective compliance with
random allocation, adequate concealment and blinding. Bias and
confounding thus seem to be the likely explanation for our find-
ings.
Second, for combining studies, it is important that the outcome
measures are comparable. Of note, trials included in this analysis
reported outcomes quite differently from each other. This could
have resulted in higher risk of bias due to selective reporting in these
trials. However, we pooled them separately, wherever possible, to
minimise this bias.
Potential biases in the review process
We undertook a systematic, thorough search of the literature to
identify all studies meeting the inclusion criteria and we are con-
fident that the included trials met the set criteria. Study selection
and data extraction were carried out in duplicate and indepen-
dently and we reached consensus by discussing any discrepancies.
A protocol was published for this review. All the analyses were
specified a priori, with the exception of a post hoc analysis of the
different cut-off values for biochemistry markers.
Agreements and disagreements with other
studies or reviews
Previous observational studies have suggested that higher folate
status in pregnancy is associated with higher birthweight, higher
placental weight, and prolonged gestation (Goldenberg 1992;
Neggers 1997;Tamura 1992). Preconception folic acid supple-
mentation has also shown effects on decreasing preterm births
(Bukowski 2009). However, the findings from this review are in-
conclusive.
A review on folic acid supplementation during pregnancy by
Charles et al (Charles 2005b) that included results from large ran-
domised controlled trials found no conclusive evidence of bene-
fit for folic acid supplementation in pregnant women. An earlier
version of this Cochrane review also reached the same conclusion
(Mahomed 1997).
A U T H O R S ’ C O N C L U S I O N S
Implications for practice
Our meta-analysis of folic acid supplementation in pregnancy in-
cluded 31 studies and provided non-conclusive evidence of folic
acid supplementation for pregnant women on pregnancy out-
comes except for improvement in mean birthweight. A reduction
14Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
in the risk of megaloblastic anaemia and improvement in folate
levels, however, has been noted with folic acid supplementation
against supplementation with placebo but the limitation to this
finding is the few number of studies reporting the outcome.
Implications for research
More well-designed, large scale randomised controlled trials are
needed to establish the benefit of folic acid supplementation dur-
ing pregnancy. Researchers of future trials should also make ef-
forts to describe the participants in more detail before enrolment
and should undertake long-term follow-up of the participants and
their children in order to study the long-term effects of folic acid
supplementation. Bias should also be reduced by adequate ran-
domisation and allocation concealment of the assignment of in-
tervention by achieving blinding of the participants, providers and
the outcome assessors and by minimising loss to follow-up of the
participants, in order to produce trials of adequate methodological
quality.
A C K N O W L E D G E M E N T S
We thank Kate Barton and Rebecca Gainey as translators of Lira
1989; Elena Intra as translator of Polatti 1992; Alison Ledward
as translator of Weil 1977, Austin Anderson Leirvik as translator
of Tchernia 1982 and Caroline Summers as translator of Balmelli
1974 and Roth 1980.
As part of the pre-publication editorial process, this review has
been commented on by three peers (an editor and two referees
who are external to the editorial team), a member of the Pregnancy
and Childbirth Group’s international panel of consumers and the
Group’s Statistical Adviser.
R E F E R E N C E S
References to studies included in this review
Balmelli 1974 {published data only}
Balmelli GP, Huser HJ. Folic acid deficiency in pregnant
women in Switzerland [Zur Frage des Folsäuremangels bei
Schwangeren in der Schweiz]. Schweizerische Medizinische
Wochenschrift 1974;104(10):351–6.
Batu 1976 {published data only}
Batu AT, Toe T, Pe H, Nyunt KK. A prophylactic trial
of iron and folic acid supplements in pregnant Burmese
women. Israel Journal of Medical Sciences 1976;12:1410–7.
Baumslag 1970 {published data only}
Baumslag N, Edelstein T, Metz J. Reduction of incidence
of prematurity by folic acid supplementation in pregnancy.
British Medical Journal 1970;1:16–7.
Blot 1981 {published data only}
Blot I, Papiernik E, Kaltwasser JP, Werner E, Tchernia G.
Influence of routine administration of folic acid and iron
during pregnancy. Gynecologic and Obstetric Investigation
1981;12:294–304.
Castren 1968 {published data only}
Castren O, Levanto A, Rauramo L, Ruponen S. Preventive
iron and folic acid therapy in pregnancy. Annales Chirurgiae
et Gynaecologiae Fenniae 1968;57:382–6.
Chanarin 1965 {published data only}
Chanarin I, Rothman D, Berry V. Iron deficiency and its
relation to folic-acid status in pregnancy: results of a clinical
trial. British Medical Journal 1965;1:480–5.
Chanarin 1968 {published data only}
Chanarin I, Rothman D, Ward A, Perry J. Folate status and
requirement in pregnancy. British Medical Journal 1968;2:
390–4.
Charles 2005 {published data only}
Charles D, Ness AR, Campbell D, Smith GD, Hall MH.
Taking folate in pregnancy and risk of maternal breast
cancer. BMJ 2004;329(7479):1375–6.
Charles DHM, Ness AR, Campbell D, Smith GD,
Whitely E, Hall MH. Folic acid supplements in pregnancy
and birth outcome: re-analysis of a large randomised
controlled trial and update of Cochrane review. Pediatric
and Perinatal Epidemiology 2005;19:112–24.
Hall M. Assessment of the effects of folic acid deficiency in
pregnancy. [MD thesis]. University of Aberdeen, 1970.
Hall MH. Folic acid deficiency and abruptio placentae.
Journal of Obstetric and Gynaecology 1972;79:222–5.
Hall MH, Pirani BB, Campbell D. The cause of the fall
in serum folate in normal pregnancy. British Journal of
Obstetrics and Gynaecology 1976;83:132–6.
Chisholm 1966 {published data only}
Chisholm M. A controlled clinical trial of prophylactic
folic acid and iron in pregnancy. Journal of Obstetrics and
Gynaecology of the British Commonwealth 1966;73:191–6.
Christian 2003 {published data only}
Christian P, Darmstadt GL, Wu L, Khatry SK, Leclerq
SC, Katz J, et al.The effect of maternal micronutrient
supplementation on early neonatal morbidity in rural
Nepal: a randomised, controlled, community trial. Archives
of Disease in Childhood. Fetal and Neonatal Edition 2008;93
(8):660–4.
Christian P, Jiang T, Khatry SK, LeClerq SC, Shrestha SR,
West Jr KP. Antenatal supplementation with micronutrients
and biochemical indicators of status and subclinical
infection in rural Nepal. American Journal of Clinical
Nutrition 2006;83:788–94.
Christian P, Khatry SK, Katz J, Pradhan EK, LeClerq
15Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
SC, Shrestha SR, et al.Effects of alternative maternal
micronutrient supplements on low birth weight in rural
Nepal: double blind randomised community trial. BMJ
2003;326(7389):571.
Christian P, Khatry SK, LeClerq SC, Dali SM. Effects of
prenatal micronutrient supplementation on complications
of labor and delivery and puerperal morbidity in rural
Nepal. International Journal of Gynecology & Obstetrics
2009;106(1):3–7.
Christian P, Murray-Kolb LE, Khatry SK, Katz J, Schaefer
BA, Cole PM, et al.Prenatal micronutrient supplementation
and intellectual and motor function in early school-aged
children in Nepal. JAMA 2010;304(24):2716–23.
Christian P, Shrestha J, LeClerq SC, Khatry SK, Jiang T,
Wagner T, et al.Supplementation with micronutrients in
addition to iron and folic acid does not further improve
the hematologic status of pregnant women in rural Nepal.
Journal of Nutrition 2003;133(11):3492–8.
Christian P, Stewart CP, LeClerq SC, Wu L, Katz J, West
KPJ, et al.Antenatal and postnatal iron supplementation
and childhood mortality in rural Nepal: a prospective
follow-up in a randomized, controlled community trial.
American Journal of Epidemiology 2009;170(9):1127–36.
Christian P, West KP, Khatry SK, Leclerq SC, Pradhan
EK, Katz J, et al.Effects of maternal micronutrient
supplementation on fetal loss and infant mortality: a
cluster-randomized trial in Nepal. American Journal of
Clinical Nutrition 2003;78(6):1194–202.
Katz J, Christian P, Dominici F, Zeger SL. Treatment
effects of maternal micronutrient supplementation vary by
percentiles of the birth weight distribution in rural Nepal.
Journal of Nutrition 2006;136(5):1389–94.
Nanayakkara-Bind A, Schulze K, Wu L, Le SC, Khatry
SK, Christian P. Effects of antenatal micronutrient
supplementation on cortisol and erythropoietin in pregnant
Nepalese women. FASEB Journal 2011;25:779.15.
Stewart CP, Christian P, LeClerq SC, West KPJ, Khatry SK.
Antenatal supplementation with folic acid + iron + zinc
improves linear growth and reduces peripheral adiposity
in school-age children in rural Nepal. American Journal of
Clinical Nutrition 2009;90(1):132–40.
Stewart CP, Christian P, Schulze KJ, Arguello M, Leclerq
SC, Khatry SK, et al.Low maternal vitamin B-12 status
is associated with offspring insulin resistance regardless of
antenatal micronutrient supplementation in rural Nepal.
Journal of Nutrition 2011;141(10):1912–7.
Stewart CP, Christian P, Schulze KJ, Leclerq SC, West
KPJ, Khatry SK. Antenatal micronutrient supplementation
reduces metabolic syndrome in 6- to 8-year-old children in
rural Nepal. Journal of Nutrition 2009;139(8):1575–81.
Dawson 1962 {published data only}
Dawson DW, More JRS, Aird DC. Prevention of
megaloblastic anaemia in pregnancy by folic acid. Lancet
1962;2:1015–20.
Decsi 2005 {published data only}
Broekaert I, Campoy C, Iznaola C, Hoffman B, Mueller-
Felber W, Koletzko BV. Visual evoked potentials in infants
after dietary supply of docosahexaenoic acid and 5-methyl-
tetrahydrofolate during pregnancy. Journal of Pediatric
Gastroenterology and Nutrition 2004;39(Suppl 1):S33.
Campoy C, Escolano-Margarit MV, Ramos R, Parrilla-
Roure M, Csabi G, Beyer J, et al.Effects of prenatal fish-oil
and 5-methyltetrahydrofolate supplementation on cognitive
development of children at 6.5 y of age. American Journal of
Clinical Nutrition 2011;94(6 Suppl):1880S–8S.
Campoy C, Marchal G, Decsi T, Cruz M, Szabo E,
Demmelmair H, et al.Spanish pregnant women’s plasma
phospholipids LC-PUFAs concentrations and its influence
on their newborns. Journal of Pediatric Gastroenterology and
Nutrition 2004;39(Suppl 1):S11.
Decsi T, Campoy C, Koletzko B. Effect of n-3
polyunsaturated fatty acid supplementation in pregnancy:
the nuheal trial. Advances in Experimental Medicine &
Biology 2005;569:109–13.
Demmelmair H, Klingler M, Campoy C, Decsi T, Koletzko
B. Low eicosapentaenoic acid concentrations in fish oil
supplements do not influence the arachidonic acid contents
in placental lipids. Journal of Pediatric Gastroenterology and
Nutrition 2004;39(Suppl 1):S11.
Demmelmair H, Klingler M, Campoy C, Diaz J, Decsi
T, Veszpremi B, et al.The influence of habitual diet and
increased docosahexaenoic acid intake during pregnancy on
the fatty acid composition of individual placental lipids
[abstract]. Journal of Pediatric Gastroenterology & Nutrition
2005;40(5):622–3.
Dolz V, Campoy C, Molloy A, Scott J, Marchal G, Decsi
T, et al.Homocysteine, folate & methylenetetrahydrofolate
reductase (MTHFR) 677 - T poly-morphism in Spanish
pregnant woman and in their offspring [abstract]. Journal of
Pediatric Gastroenterology & Nutrition 2005;40(5):623–4.
Franke C, Demmelmair H, Decsi T, Campoy C, Cruz
M, Molina-Font JA, et al.Influence of fish oil or folate
supplementation on the time course of plasma redox
markers during pregnancy. British Journal of Nutrition
2010;103(11):1648–56.
Krauss-Etschmann S, Shadid R, Campoy C, Hoster E,
Demmelmair H, iménez M, et al.Nutrition and Health
Lifestyle (NUHEAL) Study Group. Effects of fish-oil and
folate supplementation of pregnant women on maternal and
fetal plasma concentrations of docosahexaenoic acid and
eicosapentaenioc acid: a European randomised multicenter
trial. American Journal of Clinical Nutrition 2007;85(5):
1392–400.
Edelstein 1968 {published data only}
Edelstein T, Stevens K, Baumslag N, Metz J. Folic acid
and vitamin B12 supplementation during pregnancy in a
population subsisting on a sub-optimal diet. Journal of
Obstetrics and Gynaecology of the British Commonwealth
1968;75:133–7.
Fleming 1968 {published data only}
Fleming AF, Hendrickse JP, Allan NC. The prevention of
megaloblastic anaemia in pregnancy in Nigeria. Journal
of Obstetrics and Gynaecology of the British Commonwealth
1968;75(4):425–32.
16Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Fletcher 1971 {published data only}
Fletcher J, Gurr A, Fellingham FR, Prankerd TAJ, Brant
HA, Menzies DN. The value of folic acid supplements
in pregnancy. Journal of Obstetrics and Gynaecology of the
British Empire 1971;78:781–5.
Giles 1971 {published data only}
Giles PF, Harcourt AG, Whiteside MG. The effect of
prescribing folic acid during pregnancy on birthweight
and duration of pregnancy. A double blind trial. Medical
Journal of Australia 1971;2:17–21.
Harrison 1985 {published data only}
Fleming AF, Ghatoura GBS, Harrison KA, Briggs ND,
Dunn DT. The prevention of anaemia in pregnancy in
primigravidae in the guinea savanna of Nigeria. Annals of
Tropical Medicine and Parasitology 1986;80:211–33.
Fleming AF, Ludwig H, Thomsen K. Anaemia in pregnancy
in the Guinea Savanna of Nigeria. Gynecology and
Obstetrics. Berlin: Springer-Verlag, 1986:122–4.
Harrison KA, Fleming AF, Briggs ND, Rossiter CE.
Child-bearing, health and social priorities: a survey of
22,774 consecutive hospital births in Zaria, Northern
Nigeria. 5. Growth during pregnancy in Nigerian teenage
primigravidae. British Journal of Obstetrics and Gynaecology
1985;92(5):32–9.
Hibbard 1969a {published data only}
Hibbard BM, Hibbard ED. The prophylaxis of folate
deficiency in pregnancy. Acta Obstetricia et Gynecologica
Scandinavica 1969;48:339–48.
Iyengar 1975 {published data only}
Iyengar L. Effect of folic acid supplementation on birth
weight of infants. American Journal of Obstetrics and
Gynaecology 1974;122:332–6.
Iyengar L. Folic acid requirements of Indian pregnant
women. American Journal of Obstetrics and Gynecolog y 1971;
111(1):13–6.
Iyengar L, Apte SV. Prophylaxis of anemia in pregnancy.
American Journal of Clinical Nutrition 1970;23(6):725–30.
Lira 1989 {published data only}
Lira P, Barrena N, Foradori A, Gormaz G, Grebe G. Folate
deficiency in pregnancy: effect of supplementary folic
acid [Deficienca de folatos en el embarazo: efecto de una
suplementacion con acido folico]. Sangre 1989;34(1):24–7.
Menon 1962 {published data only}
Menon MKK, Rajan L. Prophylaxis of anaemia in
pregnancy. Journal of Obstetrics and Gynaecology of India
1962;12:382–9.
Metz 1965 {published data only}
Metz J, Festenstein H, Welch P. Effect of folic acid and
vitamin B12 supplementation on test of folate and Vitamin
B12 nutrition in pregnancy. American Journal of Clinical
Nutrition 1965;16:472–9.
Pack 1980 {published data only}
Pack ARC, Thomson ME. Effects of folic acid (FA)
supplementation on gingivitis in pregnancy. Journal of
Dental Research 1980;59(D1):1777.
Pack ARC, Thomson ME. Effects of topical and systemic
folic acid supplementation on gingivitis in pregnancy.
Journal of Clinical Periodontology 1980;7:402–14.
Rae 1970 {published data only}
Rae PG, Robb PM. Megaloblastic anaemia of pregnancy: a
clinical and laboratory study with particular reference to
the total and labile serum folate levels. Journal of Clinical
Pathology 1970;23:379–91.
Rolschau 1979 {published data only}
Rolschau J, Date J, Kristoffersen K. Folic acid supplement
and intrauterine growth. Acta Obstetricia et Gynecologica
Scandinavica 1979;58:343–6.
Roth 1980 {published data only}
Roth F, Mauracher E. Folic acid treatment during pregnancy
[Folsauresubstitution bei schwangeren]. Geburtshilfe und
Frauenheilkunde 1980;40:253–8.
Srisupandit 1983 {published data only}
Srisupandit S, Pootrakul P, Areekul S, Neungton
S, Mokkaves J, Kiriwat O, et al.A prophylactic
supplementation of iron and folate in pregnancy. Southeast
Asian Journal of Tropical Medicine and Public Health 1983;
14:317–23.
Tchernia 1982 {published and unpublished data}
Tchernia G, Blot I, Rey A, Kaltwasser JP, Zittoun J,
Papiernik E. Maternal folate status, birthweight and
gestational age. Developmental Pharmacology Therapeutics
1982;4:58–65.
Trigg 1976 {published data only}
Trigg KH, Rendall EJC, Johnson A, Fellingham FR,
Prankerd TAJ. Folate supplements during pregnancy.
Journal of the Royal College of General Practitioners 1976;26:
228–30.
Weil 1977 {published data only}
Weil A, Mauracher E. Folic acid and pregnancy, a real
problem? [Acide folique et gravidité, problème réel?].
Schweizer Medizinische Wochenschrift 1977;107:1943–7.
Willoughby 1967 {published data only}
Willoughby ML. An investigation of folic acid
requirements in pregnancy. II. British Journal of Hematology
1967;13(4):503–9.
Willoughby ML, Jewell FJ. Investigation of folic acid
requirements in pregnancy. British Medical Journal 1966;2
(5529):1568–71.
Willoughby MLN, Jewell FG. Folate status throughout
pregnancy and in postpartum period. British Medical
Journal 1968;4:356–60.
References to studies excluded from this review
Bjerre 1967 {published data only}
Bjerre B. Study of the haematological effect of prophylactic
folic acid medicamentation in pregnancy. Acta Obstetricia et
Gynecologica Scandinavica 1967;46(4):71–85.
17Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Colman 1974 {published data only}
Colman N, Barker M, Green R, Metz J. Prevention of folate
deficiency in pregnancy by food fortification. American
Journal Clinical Nutrition 1974;27:339–44.
Colman 1975 {published data only}
Colman N, Larsen JV, Barker M, Barker EA, Green R, Metz
J. Prevention of folate deficiency by food fortification. III.
Effect in pregnant subjects of varying amounts of added
folic acid. American Journal of Clinical Nutrition 1975;28:
465–70.
Ellison 2004 {published data only}
Ellison J, Clark P, Walker ID, Greer IA. Effect of
supplementation with folic acid throughout pregnancy on
plasma homocysteine concentration. Thrombosis Research
2004;114:25–7.
Giles 1960 {published data only}
Giles C, Burton H. Observations on prevention and
diagnosis of anaemia in pregnancy. British Medical Journal
1960;2:636–40.
Gregory 2001 {published data only}
Gregory JF 3rd, Caudill MA, Opalko FJ, Bailey LB.
Kinetics of folate turnover in pregnant women (second
trimester) and nonpregnant controls during folic acid
supplementation: stable-isotopic labeling of plasma folate,
urinary folate and folate catabolites shows subtle effects of
pregnancy on turnover of folate pools. Journal of Nutrition
2001;131(7):1928–37.
Hague 1998 {published data only}
Hague B, Crowther C, Robinson J, Dekker G, Odendaal
H. Prevention of recurrent pre-eclampsia by folic acid
supplementation in women with hyperhomocysteinaemia:
proposal for a randomized trial. Netherlands Journal of
Medicine 1998;52:S24.
Hague B, Dekker G, Crowther C, Robinson J, Odendaal
H. The HOPE (hyperhomocysteinaemia in pre-eclampsia)
trial: prevention of recurrent pre-eclampsia by folic acid
supplementation in women with hyperhomocysteinemia.
Hypertension in Pregnancy 2000;19(Suppl 1):Abstract no
P10.
Hamilton 1973 {published data only}
Hamilton PJS, Gebbie DAM. Antenatal clinics as trial units
in evaluating treatment of anaemia in pregnancy. The
use and abuse of drugs and chemicals in Tropical Africa.
Proceedings of the 1973 Annual Scientific Conference of the
East African Medical Research Council. Nairobi, Kenya.:
Nairobi: East African Literature Bureau, 1973:463–6.
Hekmatdoost 2011 {published data only}
Hekmatdoost A. Comparison of the effect of folic acid and
5-methyltetrahydrofolate (5MTHF) on serum folate and
homocysteine levels, and abortion rates in women suffering
from recurrent abortion. IRCT Iranian Registry of Clinical
Trials (www.irct.ir) (accessed 8 July 2011).
Hibbard 1969 {published data only}
Hibbard BM, Hibbard ED. The treatment of folate
deficiency in pregnancy. Acta Obstetricia et Gynecologica
Scandinavica 1969;48:349–56.
Khanna 1977 {published data only}
Khanna S, Dube B, Kumar S. Anaemia of pregnancy in
northern India. Nature and therapeutic follow-up. Tropical
& Geographical Medicine 1977;29(1):24–8.
Klinger 2006 {published data only}
Klingler M, Blaschitz A, Campoy C, Cano A, Molloy
AM, Scott JM, et al.The effect of docosahexaenoic avid
and folic acid supplementation on placental apoptosis and
proliferation. British Journal of Nutrition 2006;96(1):
182–90.
Kristoffersen 1979 {published data only}
Kristoffersen K, Rolschau J, Date JV, Honore E. The
influence of folic acid supplement on intrauterine growth
[abstract]. 9th World Congress of Gynecology and
Obstetrics;Tokyo, Japan; 1979 October 26-31. 1979:242.
Ma 2008 {published data only}
Ma AG, Schouten EG, Zhang FZ, Kok FJ, Yang F, Jiang
DC, et al.Retinol and riboflavin supplementation decreases
the prevalence of anaemia in Chinese pregnant women
taking iron and folic acid supplements. Journal of Nutrition
2008;138(10):1946–50.
Manizheh 2009 {published data only}
Manizheh SM, Mandana S, Hassan A, Amir GH, Mahlisha
KS, Morteza G. Comparison study on the effect of prenatal
administration of high dose and low dose folic acid. Saudi
Medical Journal 2009;30(1):88–97.
Melli 2008 {published data only}
Melli MS, Shojaiee M, Sheshvan MK. Prenatal
administration of high dose and low dose of folic acid
on maternal plasma homocysteine concentration and its
relationship to the development of preeclampsia. Journal of
Maternal-Fetal and Neonatal Medicine 2008;21(Suppl 1):82.
Ouma 2006 {published data only}
Ouma P, Parise ME, Hamel MJ, ter Kuile FO, Otieno
K, Ayisi JG, et al.A randomised controlled trial of folate
supplementation when treating malaria in pregnancy with
sulfadoxine-pyrimethamine. PLoS Clinical Trials 2006;1
(6):e28.
van Eijk AM, Ouma PO, Williamson J, ter Kuile FO,
Parise M, Otieno K, et al.Plasma folate level and high-dose
folate supplementation predict sulfadoxine-primethamine
treatment failure in pregnant women in Western Kenya who
have uncomplicated malaria. Journal of Infectious Diseases
2008;198(10):1550–3.
Polatti 1992 {published data only}
Polatti F, Perotti F, Nappi R, Prandi P. Calcium folinate
in pregnancy: therapeutic efficacy [Calcio folinato in
gravidanza]. Minerva Ginecologica 1992;44:33–7.
Taylor 1979 {published data only}
Taylor DJ, Lind T. Red cell mass during and after normal
delivery. British Journal of Obstetrics and Gynaecology 1979;
86:364–70.
Taylor 1981 {published data only}
Taylor DJ, Lind T. Pueperal haematological indices. British
Journal of Obstetrics and Gynaecology 1981;88:601–6.
18Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Tchernia 1982a {published data only}
Tchernia G, Blot I, Rey A, Papiernik E. Maternal iron and
folate deficiencies. Incidence on the newborn. Annales de
Pediatrie 1982;29:276–80.
Thomson 1982 {published data only}
Thomson ME, Pack ARC. Effects of extended systemic
and topical folate supplementation on gingivitis of
pregnancy. Journal of Clinical Periodontology 1982;9:
275–80.
Thomson ME, Pack ARC. Systemic folic acid (F.A.)
supplementation and effects of pregnancy gingivitis. Journal
of Dental Research 1981;60:1072.
Ulrich 1999 {published data only}
Ulrich M, Kristoffersen K, Rolschau J, Grinsted P,
Schaumburg E, Foged N. The influence of folic acid
supplement on the outcome of pregnancies in the county
of Funen in Denmark. Part II. Congenital anomalies.
A randomised study. European Journal of Obstetrics &
Gynecology and Reproductive Biology 1999;87(2):111–3.
Wang 2012 {published data only}
Wang W, Yan H, Zeng L, Cheng Y, Wang D, Li Q. No
effect of maternal micronutrient supplementation on early
childhood growth in rural western China: 30 month
follow-up evaluation of a double blind, cluster randomized
controlled trial. European Journal of Clinical Nutrition
2012;66(2):261–8.
Zeng 2008 {published data only}
Zeng L, Dibley MJ, Cheng Y, Dang S, Chang S, Kong
L, et al.Impact of micronutrient supplementation during
pregnancy on birth weight, duration of gestation, and
perinatal mortality in rural western China: double blind
cluster randomised controlled trial. BMJ 2008;337:a2001.
Zeng L, Yan H, Cheng Y, Dang S, Dibley MJ. Adherence
and costs of micronutrient supplementation in pregnancy in
a double-blind, randomized, controlled trial in rural western
China. Food and Nutrition Bulletin 2009;30(4):S480–7.
References to ongoing studies
Wen 2012 {published data only}
Wen SW. Effect of folic acid supplementation in pregnancy
on pre-eclampsia - folic acid clinical trial (FACT). Current
Controlled Trials (http://www.current-trials.com) (accessed
8 July 2011).
Wen SW, Champagne J, Rennicks R, Walker M. Effect of
folic acid supplementation in pregnancy on preeclampsia
- Folic acid clinical trial (FACT). Pregnancy Hypertension
2012;2(3):180.
Wen SW, Walker M. Effect of folic acid supplementation in
pregnancy on preeclampsia. Pregnancy Hypertension 2010;1
(Suppl 1):S28.
Additional references
Açkurt 1995
Açkurt F, Wetherilt H, Löker M, Hacibekiro M.
Biochemical assessment of nutritional status in pre- and
post-natal Turkish women and outcome of pregnancy.
European Journal of Clinical Nutrition 1995;49:613–22.
Bailey 1995
Bailey LB. Folate requirements and dietary
recommendations. In: Bailey LB editor(s). Folate in Health
and Disease. New York: Marcel Dekker, 1995:123–52.
Bates 1986
Bates CJ, Fuller NJ, Prentice AM. Folate status during
pregnancy and lactation in a West African rural community.
Human Nutrition. Clinical Nutrition 1986;40:3–13.
Botto 1996
Botto LD, Khoury MJ, Mulinare J, Erickson JD.
Periconceptional multivitamin use and the occurrence of
conotruncal heart defects: results from a population based,
case-control study. Pediatrics 1996;98(5):911–7.
Bruinse 1995
Bruinse HW, Van den Berg H. Changes of some vitamin
levels during and after normal pregnancy. European Journal
of Obstetrics & Gynecology and Reproductive Biology 1995;
61:31–7.
Bukowski 2009
Bukowski R, Malone FD, Porter FT, Nyberg DA,
Comstock CH, Hankins GDV, et al.Preconception folate
supplementation and the risk of spontaneous preterm
birth: prospective cohort study. PLoS Medicine 2009;6(5):
e1000061.
Caudill 1998
Caudill MA, Gregory JF III, Hutson AD, Bailey LB. Folate
catabolism in pregnant and nonpregnant women with
controlled folate intakes. Journal of Nutrition 1998;128(2):
204–8.
Chanarin 1969
Chanarin I. The Megaloblastic Anemias. London, United
Kingdom: Blackwell Scientific, 1969:786–829.
Charles 2005b
Charles DHM, Ness AR, Campbell D, Smith GD, Whitely
E, Hall MH. Folic acid supplements in pregnancy and birth
outcome: re-analysis of a large randomised controlled trial
and update of Cochrane review. Pediatric and Perinatal
Epidemiology 2005;19:112–24.
Czeizel 1992
Czeizel AE, Dudas I. Prevention of the first occurrence
of neural-tube defects by periconceptional vitamin
supplementation. New England Journal of Medicine 1992;
327(26):1832–5.
Czeizel 1993
Czeizel AE. Prevention of congenital abnormalities by
periconceptional multivitamin supplementation. BMJ
1993;306(6893):1645–8.
Czeizel 1996
Czeizel AE. Reduction of urinary tract and cardiovascular
defects by periconceptional multivitamin supplementation.
American Journal of Medical Genetics 1996;62(2):179–83.
19Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
De Benoist 2008
De Benoist B. Conclusions of a WHO Technical
Consultation on folate and vitamin B12 deficiencies. Food
Nutrition Bulletin 2008;29(Suppl 2):S238–S244.
De-Regil 2010
De-Regil LM, Fernández-Gaxiola AC, Dowswell T, Peña-
Rosas JP. Effects and safety of periconceptional folate
supplementation for preventing birth defects. Cochrane
Database of Systematic Reviews 2010, Issue 10. [DOI:
10.1002/14651858.CD007950.pub2]
Dietary Ref 1998
Anonymous. Dietary Reference Intakes for Thiamin,
Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12,
Pantothenic acid, Biotin and Choline. Institute of Medicine,
1998.
Fleming 1972
Fleming AF. Urinary excretion of folate in pregnancy.
Journal of Obstetrics and Gynaecology of the British
Commonwealth 1972;79:916–20.
Food and Nutrition Board 1970
Food, Nutrition Board. National Research Council.
Maternal Nutrition and the Course of Pregnancy. Washington,
DC: National Academy of Sciences, 1970.
Food and Nutrition Board 1998
Food, Nutrition Board. Institute of Medicine. Dietary
Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin
B6, Folate, Vitamin B12, Pantothenic Acid, Biotin and
Choline. Washington, DC: National Academy Press, 1998.
Goldenberg 1992
Goldenberg RL, Tamura T, Cliver SP, Cutter GR, Hoffman
HJ, Copper RL. Serum folate and fetal growth retardation:
a matter of compliance?. Obstetrics and Gynecology 1992;
79:719–22.
Green 1995
Green R, Jacobsen DW. Clinical implications of
hyperhomocysteinemia. In: Bailey LB editor(s). Folate in
Health and Disease. Newyork (NY): Marcel Dekker, 1995:
75–122.
Gregory 2001b
Gregory JF III, Caudill MA, Opalko J, Bailey LB. Kinetics
of folate turnover in pregnant women (second trimester) and
nonpregnant controls during folic acid supplementation:
stable-isotopic labelling of plasma folate, urinary folate
and folate catabolites shows subtle effects of pregnancy on
turnover of folate pools. Journal of Nutrition 2001;131:
1928–37.
Haider 2006
Haider BA, Bhutta ZA. Multiple-micronutrient
supplementation for women during pregnancy. Cochrane
Database of Systematic Reviews 2006, Issue 4. [DOI:
10.1002/14651858.CD004905.pub2]
Herbert 1997
Herbert V, Bigaoutte J. Call for endorsement of a petition
to the Food and Drug Administration to always add vitamin
B-12 to any folate fortification or supplement. American
Journal of Clinical Nutrition 1997;65(2):572–3.
Higgins 2000
Higgins JR, Quinlivan EP, McPartlin J, Scott JM, Weir
DG, Darling MRN. The relationship between increased
folate catabolism and the increased requirement for folate in
pregnancy. BJOG: an international journal of obstetrics and
gynaecology 2000;107:1149–54.
Higgins 2011
Higgins JPT, Green S, editors. Cochrane Handbook for
Systematic Reviews of Interventions Version 5.1.0 [updated
March 2011]. The Cochrane Collaboration, 2011.
Available from www.cochrane-handbook.org.
Institute of Medicine 2000
Institute of Medicine. Dietary Reference Intakes for Thiamin,
Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12,
Pantothenic Acid, Biotin and Choline. Washington, DC:
National Academy Press, 2000:196–305.
Krishnaswamy 2001
Krishnaswamy K, Nair KM. Importance of folate in human
nutrition. British Journal of Nutrition 2001;85:S115–S124.
Landon 1971
Landon MJ, Hytten FE. The excretion of folate in
pregnancy. Journal of Obstetrics and Gynaecology of the
British Commonwealth 1971;78:769–75.
Lawson 1988
Lawson JB. Anaemia in pregnancy. In: Lawson JB, Stewart
DB editor(s). Obstetrics and Gynaecology in the Tropics and
Developing Countries. London: Edward Arnold, 1988:76–8.
Li 1995
Li DK, Daling JR, Mueller BA, Hickik DE, Fantel AG,
Weiss NS. Periconceptional multivitamin use in relation to
the risk of congenital urinary tract anomalies. Epidemiology
1995;6(3):212–8.
Makedos 2007
Makedos G, Papanicolaou A, Hitoglou A, Kalogiannidis
I, Makedos A, Vrazioti V, et al.Homocysteine, folic acid
and B12 serum levels in pregnancy complicated with
preeclampsia. Archives of Gynecology and Obstetrics 2007;
275(2):121-4.
McPartlin 1993
McPartlin J, Halligan A, Scott JM, Darling M, Weir DG.
Accelerated folate breakdown in pregnancy. Lancet 1993;
341(8838):148–9.
Morrison 1998
Morrison K, Papapetrou C, Hol FA, Mariman EC, Lynch
SA, Burn J, et al.Susceptibility to spina bifida; an association
study of five candidate genes. Annals of Human Genetics
1998;62(5):379–96.
MRC 1991
MRC Vitamin Study Research Group. Prevention of neural
tube defects: results of the Medical Research Council
Vitamin Study. Lancet 1991;338(8760):131–7.
Neggers 1997
Neggers YH, Goldenberg RL, Tamura T, Cliver SP, Hoffman
HJ. The relationship between maternal dietary intake
20Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
and infant birthweight. Acta Obstetricia et Gynecologica
Scandinavica 1997;165:71–5.
NICE 2008
National Institute for Health and Clinical Excellence.
NICE public health guidance 11: Improving the nutrition
of pregnant and breastfeeding mothers and children in low-
income households. London: NICE, 2011 July.
Patrick 2004
Patrick TE, Powers RW, Daftary AR, Ness RB, Roberts JM.
Homocysteine and folic acid are inversely related in black
women with preeclampsia. Hypertension 2004;43(6):1279-
82.
Pena-Rosas 2006
Pena-Rosas JP, Viteri FE. Effects of routine oral
iron supplementation with or without folic acid for
women during pregnancy. Cochrane Database of
Systematic Reviews 2006, Issue 3. [DOI: 10.1002/
14651858.CD004736.pub2]
Refsum 2008
Refsum H, Smith AD. Are we ready for mandatory
fortification withvitamin B-12?. American Journal of
Clinical Nutrition 2008;88(2):253-4.
RevMan 2011
The Nordic Cochrane Centre, The Cochrane Collaboration.
Review Manager (RevMan). 5.1. Copenhagen: The Nordic
Cochrane Centre, The Cochrane Collaboration, 2011.
Rush 1994
Rush D. Periconceptional folate and neural tube defect.
American Journal of Clinical Nutrition 1994;59(Suppl 1):
511S–515S.
Scholl 2000
Scholl TO, Johnson WG. Folic acid: influence on the
outcome of pregnancy. American Journal of Clinical
Nutrition 2000;71:1295–303.
Selhub 1993
Selhub J, Jacques PF, Wilson PWF, Rush D, Rosenberg
IH. Vitamin status and intake as primary determinants of
homocysteinemia in an elderly population. JAMA 1993;
270:2693–8.
Shaw 1995
Shaw GM, Lammer EJ, Wasserman CR, O’Malley CD,
Tolarova MM. Risks of orofacial clefts in children born
to women using multivitamins containing folic acid
periconceptionally. Lancet 1995;346(8972):393–6.
Smith 1983
Smith AM, Picciano MF, Deering RH. Folate
supplementation during lactation: maternal folate status,
human milk folate content, and their relationship to infant
folate status. Journal of Pediatric Gastroenterology and
Nutrition 1983;2:622–8.
Smits 2001
Smits LJM, Essed GGM. Short interpregnancy intervals and
unfavourable pregnancy outcome: role of folate depletion.
Lancet 2001;358:2074–7.
Tamura 1992
Tamura T, Goldenberg RL, Freeberg LE, Cliver SP,
Cutter GR, Hoffman HJ. Maternal serum folate and
zinc concentrations and their relationships to pregnancy
outcome. American Journal of Clinical Nutrition 1992;56:
365–70.
Tamura 2006
Tamura T, Picciano MF. Folate and human reproduction.
American Journal of Clinical Nutrition 2006;83(5):93–1016.
Willoughby 1968
Willoughby MLN. Folate status throughout pregnancy and
in post partum period. British Medical Journal 1968;4:
356–60.
References to other published versions of this review
Mahomed 1995
Mahomed K. Routine folate supplementation in pregnancy.
[revised 28 April 1993]. In: Enkin MW, Keirse MJNC,
Renfrew MJ, Neilson JP, Crowther C (eds.) Pregnancy and
Childbirth Module. In: The Cochrane Pregnancy and
Childbirth Database [database on disk and CDROM]. The
Cochrane Collaboration; Issue 2, Oxford: Update Software;
1995.
Mahomed 1997
Mahomed K. Folate supplementation in pregnancy.
Cochrane Database of Systematic Reviews 1996, Issue 3.
[DOI: 10.1002/14651858.CD000183.pub2]
Indicates the major publication for the study
21Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
C H A R A C T E R I S T I C S O F S T U D I E S
Characteristics of included studies [ordered by study ID]
Balmelli 1974
Methods It was a RCT in which women were randomised into 2 groups and recruited fromClinic
for Female Medicine at the University of Bern (Switzerland). Average age for iron group
was 27.8 years while for Iron + folic acid group was 26.9 years. Measurement were taken
over the period of 12 weeks. Blood samples were taken at monthly intervals
Participants Pregnant women between 20-25 weeks of pregnancy (n = 42).
Interventions Group 1: ferrous sulphate 125 mg + vitamin B12 100 µg (n = 21)
Group 2: ferrous sulphate 125 mg + folic acid 100 µg + vitamin B12 100 µg (n = 21)
Outcomes Pre-delivery haemoglobin level (n = 42), serum folate level (n = 42)
Notes All the women were the residents of Switzerland for longer than a year. Participants were
restricted to patients with a haemoglobin level between 10-12 g%, suspected abnormal
pregnancies or patients suffering from intercurrent illness were excluded from study
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Adequate sequence generation was not de-
scribed in the text.
Allocation concealment (selection bias) High risk Quote “ women were randomised into two
groups”.
Comment: probably not done.
Blinding (performance bias and detection
bias)
All outcomes
High risk Treatment was not blinded.
Incomplete outcome data (attrition bias)
All outcomes
Low risk Reasons for exclusion were described. At-
trition (21%) with reasons were mentioned
in the study
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judge-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
22Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Batu 1976
Methods This RCT was conducted on Burmese women. Women were randomly placed into the
treatment groups. Venous blood was collected before the commencement of treatment,
near full term (38th to 40th week), and 4 to 7 weeks after birth
Participants Women attending antenatal clinic in Rangoon for their antenatal visit (n = 96)
Interventions Group1: iron 60 mg (n = 30).
Group2: iron 60 mg+ folic acid 5 mg (n = 25).
Group3: placebo (n = 22).
Group4: folic acid 5 mg (n = 19).
Outcomes Pre-delivery haemoglobin level (n = 46).
Notes For this review we compared group 2 with group 1 and group 3 with group 4
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “women were randomly placed to
one of four treatment regimens
Allocation concealment (selection bias) Unclear risk The methods used for allocation conceal-
ment was not stated in the text
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Blinding was not described in the text.
Incomplete outcome data (attrition bias)
All outcomes
High risk Exclusion number and reasons were not de-
scribed the text, while attrition (69%) was
given with reasons
Selective reporting (reporting bias) Unclear risk Insufficient information to make any
judgement.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Baumslag 1970
Methods This was a randomised trial conducted on all pregnant women who were attending
antenatal clinics at the Baragwanath and South Rand Hospitals, Johannesburg (South
Africa). Pregnant women were allocated into 3 interventions groups based on random
numbers
23Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Baumslag 1970 (Continued)
Participants All pregnant women attending antenatal clinics at Baragwanath and South Rand Hos-
pitals, Johannesburg (n = 355)
Interventions Group 1 received 200 mg of iron by mouth (n = 115).
Group 2 received 5 mg of folic acid daily by mouth in addition to the iron (n = 127)
Group 3 received 50 µg of vitamin B12 by mouth in addition to the folic acid and iron
(n = 113)
Outcomes Birthweight was measured.
Notes Birthweight was analysed separately for Bantu participants and white participants. In
the white participants supplementation was started after the 24th week, while supple-
mentation in Bantu participants was started after 28th week
We compared the data of group 1 with group 2 only.
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “patients were allocated by random
numbers to three groups”
Allocation concealment (selection bias) Unclear risk Insufficient information about allocation
concealment.
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Insufficient information about blinding.
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information about exclusion
and attrition.
Selective reporting (reporting bias) Low risk The study has mentioned data on all out-
come measure mentioned as objective
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Blot 1981
Methods This was a RCT conducted on women coming for antenatal examination in Paris. Each
women was given a bottle containing iron or a combination thereof with folic acid. The
2 groups of women were totally comparable on their baseline characteristics
Participants All women attending for the compulsory antenatal examination at the end of 6th month
of pregnancy (n = 109)
24Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Blot 1981 (Continued)
Interventions Group1: iron 105 mg (n = 55).
Group2: iron 105 mg + folic acid 350 mg (n = 54).
Outcomes Pre-delivery haemoglobin levels (n = 109).
Notes All women were given ascorbic acid 500 mg. Study population was generally from upper
social class which may lead to underestimation of nutritional deficiencies
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “patients were given bottle of 90
tablets, contained either iron or the com-
bination of iron with folic acid”
Comment: probably not done.
Allocation concealment (selection bias) Low risk Bottle of tablets without the awareness of
intervention type was given to patients
Blinding (performance bias and detection
bias)
All outcomes
Low risk Neither the patient nor the obstetrician was
aware of the nature of treatment
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Data on exclusion with its reason were not
described in the text. Attrition (45.5%)
with reasons were reported
Selective reporting (reporting bias) Low risk Study appears to be free of selective report-
ing.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Castren 1968
Methods This RCT was conducted on pregnant women coming to the Maternity Centre of Turku
(Finland). 63 women in each groups were started on prophylactic intervention and
control treatment. Blood samples were studied 3 times: first before the institution of
therapy in the 10th to 20th week of pregnancy, second in the 21st to 30th week, and
third at the end of pregnancy in the 31st to 40th week
Participants Healthy pregnant women who at the time of examination at the centre had shown no
signs of anaemia (n = 126)
25Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Castren 1968 (Continued)
Interventions Group 1 comprised of 63 women started on 200 mg of ferrous sulphate and (n = 63)
Group 2 was started on 200 mg of ferrous sulphate and 3 mg of folic acid (n = 63)
Outcomes Pre-delivery haemoglobin level (n = 109), pre-delivery serum folate (n = 109)
Notes
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
High risk Quote: “series of patients were collected
from maternity centers of Turku and then
the series was divided into two groups”
Comment: probably not done.
Allocation concealment (selection bias) Unclear risk Insufficient information about allocation
concealment.
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Insufficient information about blinding.
Incomplete outcome data (attrition bias)
All outcomes
Low risk Number of pregnant women excluded was
not mentioned nor its reasons. Attrition
(14%) was mentioned along with its rea-
sons
Selective reporting (reporting bias) Low risk Study appears to be free of selective report-
ing.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Chanarin 1965
Methods The RCT was conducted on pregnant women coming to antenatal clinics at Saint Mary
Hospital, London
Participants Pregnant women coming to antenatal clinic (n = 144).
Interventions Women were allocated to 1 of the following 3 groups.
Group 1: ferrous fumarate 100 mg (n = 50).
Group 2: ferrous fumarate with 10 µg folic acid (n = 52).
Group 3: lactose (n = 42).
Subjects were asked to take 1 throughout pregnancy.
26Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Chanarin 1965 (Continued)
Outcomes Mean urinary excretion (n = 144), mean haemoglobin (n = 144)
Notes For this review, group 1 was compared with group 2.
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “women were allocated at random
to one of the three groups”
Allocation concealment (selection bias) High risk Insufficient information about allocation
concealment.
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “Glaxo Laboratories supplied these
drugs with green, blue or red labels and the
precise contents of each batch being un-
known to us during the trials”
Comment: investigators blinded, it seem
from the available information that it was
a single blinded study
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information.
Selective reporting (reporting bias) Unclear risk Insufficient information.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Chanarin 1968
Methods This was a RCT in which women attending the antenatal clinic at St. Mary’s hospital
(London) took part in the study
Participants 206 women took part in this study. They all were less than 16 weeks of pregnancy.
Women were given 1 g of IV Iron dextran as 4 250 mg doses at weekly intervals. At the
20th week they were assigned in to groups (n = 206)
Interventions Ferrous fumarate 260 mg (n = 101).
Ferrous fumarate 260 mg and 100 µg folic acid (n = 105).
Outcomes Changes in haemoglobin (n = 206), serum iron (n = 206), serum folate (n = 206) and
red cell folate levels (n = 206)
Notes
27Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Chanarin 1968 (Continued)
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “Allotted to one of the two groups”.
Allocation concealment (selection bias) Unclear risk Insufficient information to permit any
judgement.
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Quote: “The survey being conducted as a
blind trial”.
Comment: probably not done.
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information to permit any
judgment.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit any
judgment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Charles 2005
Methods This is a RCT in which during the period June 1966 to June 1967, women (resident of
Aberdeen city, Scotland) were identified as potentially eligible to enter into this study to
examine the effect of folic acid supplementation on pregnancy outcome
Participants All pregnant women booking for antenatal care under 30 weeks’ gestation (n = 2928)
Interventions Women were assigned into 3 groups.
Group 1: folic acid 200 µg daily doses (n = 466).
Group 2: folic acid 5 mg daily doses (n = 485).
Group 3: placebo (n = 1977).
Outcomes Birthweight, placental weight, gestational age at delivery, placenta praevia,pre-ecl ampsia,
fetal abnormality and stillbirth or neonatal deaths (n = 2819)
Notes
Risk of bias
Bias Authors’ judgement Support for judgement
28Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Charles 2005 (Continued)
Random sequence generation (selection
bias)
Unclear risk Quote: “Randomised”.
Allocation concealment (selection bias) High risk Quote: “The tablets were kept in numbered
drawers and distributed in sequence; dur-
ing the first 2 weeks of recruitment, the
tablets were not ready for distribution and
109 patients recruited at this time received
no treatment ad were therefore not eligible
for randomisation
Comment: probably not done.
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “the study was a double blinded
so neither the trial author, nor the patient
knew the code to the tablets they were re-
ceiving”
Comment: probably done.
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information to permit judge-
ment.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judge-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Chisholm 1966
Methods Women attending the antenatal clinic at their first visit before the 28th week of pregnancy
were asked to participate in a randomised clinical trial to investigate the best method of
preventing anaemia during pregnancy in Oxford (UK)
Participants Women who had haemoglobin level less than 11 g per 100 mL and serum iron of less
than 60 µg per 100 mL were not included in the trial and were treated immediately (n
= 542)
Interventions Half of the patient treated with ferrous gluconate (300 mg) 3 times daily (n = 183) and
half with placebo tablets (n = 177). These groups were again divided into 3 groups; 1
group was given 500 µg (n = 61), or a high dose of 5 mg folic acid (n = 62) or a placebo
(n = 59)
Outcomes Mean haemoglobin level (360), red cell folate level and folate levels (360)
Notes
Risk of bias
29Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Chisholm 1966 (Continued)
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “Random allocation of women to
one of the 6 treatment groups”
Allocation concealment (sel ection bias) Unclear risk Quote: “Bottles containing the tablets were
numbered by random selection
Comment: .insufficient information to
permit judgement.
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Quote: “code was not known while the pa-
tients were still on trial”
Comment: participants were blinded.
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information to permit judge-
ment.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judge-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Christian 2003
Methods The study was a cluster-randomised, double-blind trial that featured an active control
group and was conducted in the rural plains district of Sarlahi, Nepal
Participants 4926 pregnant women and their 4130 infants in rural Nepal.
Interventions In addition to vitamin A (1000 g retinol equivalents), the intervention groups received
either:
folic acid (FA; 400 g), (n = 941)
FA + iron (60 mg), (n = 957)
FA + iron + zinc (30 mg), (n = 999) or
Multiple micronutrients (MNs; the foregoing plus 10 g vitamin D, 10 mg vitamin
E, 1.6 mg thiamine, 1.8 mg riboflavin, 2.2 mg vitamin B-6, 2.6 g vitamin B-12, 100
mg vitamin C, 64 g vitamin K, 20 mg niacin, 2 mg Cu, and 100 mg Mg) (n = 1050).
The control group received vitamin A only (n = 1051).
Outcomes Perinatal deaths, Infant deaths, neonatal deaths.
Notes
Risk of bias
Bias Authors’ judgement Support for judgement
30Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Christian 2003 (Continued)
Random sequence generation (selection
bias)
Low risk Quote: “Randomization was done in
blocks of 5 within each village development
community by the senior study investiga-
tors, who drew numbered chips from a hat.
Comment: Probably done.
Allocation concealment (selection bias) Low risk Quote: “The supplements, which were of
identical shape, size, and color, arrived in
Nepal in opaque, sealed, and labelled bot-
tles coded 1-5. The code allocation was
kept locked at the Johns Hopkins Univer-
sity, Baltimore.”
Comment: Probably done.
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “The investigators, field staff, and
participants were blinded to the codes
throughout the study.”
Incomplete outcome data (attrition bias)
All outcomes
Low risk < 0.5% in all arms combined.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judge-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Dawson 1962
Methods Patients attending antenatal clinic were selected for this RCT in Crumpsall Hospital,
Manchester
Participants Women attending antenatal clinic and were at or before 28 weeks of pregnancy were
selected (n = 144)
Interventions Women were assigned to receive intervention (folic acid 15 mg ) (n = 63) or control
group (n = 81)
Outcomes Prepartum and postpartum haemoglobin levels.
Notes
Risk of bias
Bias Authors’ judgement Support for judgement
31Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Dawson 1962 (Continued)
Random sequence generation (selection
bias)
High risk Quote: “Women were allotted a group in
order in which they were booked”
Comment: probably not done.
Allocation concealment (selection bias) Unclear risk Insufficient information to permit judg-
ment.
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Insufficient information to permit judg-
ment.
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information to permit judg-
ment.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judg-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Decsi 2005
Methods This is a placebo-controlled, randomised, double-blind trial on expecting mothers living
in Germany, Hungary and Spain
Participants Expectant women from the 20th week of gestation (n = 312).
Interventions Women received either:
Group A: 500 mg Docosahexaenoic Acid (DHA) (n = 77)
Group B: or 400 mg Methyltetrahydofolate (5-MTHF) (n = 80)
Group C: or placebo (n = 80)
Group D: or the combination of 500 mg DHA and 400 mg 5-MTHF (n = 75)
Outcomes Contribution of docosahexaenoic acid (DHA) to the fatty acids of erythrocyte
phophatidylcholine (PC) and phosphatidylethanolamine (PE) lipids at delivery (n = 312)
Notes For this review, we compared group B with group C. and group A with group D
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “....randomized,...”
Comment: insufficient information to per-
mit judgment.
32Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Decsi 2005 (Continued)
Allocation concealment (selection bias) Unclear risk Insufficient information to permit judg-
ment.
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “....double blind,...”
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Insufficient information to permit judg-
ment.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judg-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Edelstein 1968
Methods Patients were Bantu (Johannesberg, South Africa) attending Baragwanath Hospital were
randomly allocated to 1 of the 2 groups in this RCT
Participants Pregnant women (n = 396).
Interventions Group1: iron 200 mg (n = 235).
Group 2: iron 200 mg + folic acid 5 mg (n = 89).
Group3: iron 200 mg, folic acid 5 mg + vit B12 50 µg (n = 72)
Outcomes Pre-delivery haemoglobin levels (n = 172), postpartum haemoglobin levels (n = 291),
pre-delivery folate levels (n = 211), postpartum folate levels (n = 291)
Notes Their diet largely contains maize. For this review we only compared group 1 with group
2
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “pregnant patients were randomly
allocated to one of the two groups”
Allocation concealment (selection bias) Low risk All tables were dispensed at identical gelatin
capsules.
Blinding (performance bias and detection
bias)
All outcomes
Low risk The type of supplementation was not
known to the participants or the laboratory
staff
33Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Edelstein 1968 (Continued)
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Exclusion and attrition (or reasons) were
not reported.
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judge-
ment.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Fleming 1968
Methods The RCT was conducted in Nigeria. Alternate women were allotted to 2 groups in the
order in which they attended the clinic
Participants Women with primigravida less than 26 weeks’ pregnant with PCV 27% or more, and
who had not received any treatment (n = 53)
Interventions Group 1: lactose based tab (n = 26), group 2: folic acid 5 mg (n = 27)
Outcomes Premature births (n = 53), folate deficiency (n = 53).
Notes All the women received antimalarials and iron supplements.
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
High risk Quote: “alternate patients were allotted to
group A or group B in the order in which
they attended the clinic”
Comment: probably not done.
Allocation concealment (selection bias) Low risk Tablets for both the groups were coloured
in the same manner
Blinding (performance bias and detection
bias)
All outcomes
Low risk The identity of the tablets was not known
to investigators until after the completion
of the trial
Incomplete outcome data (attrition bias)
All outcomes
Low risk Number of exclusions were not mentioned
(nor the reasons). Numbers of attrition
(28%) were described but their reasons
were not given in the text
Selective reporting (reporting bias) Unclear risk Insufficient information to permit judge-
ment.
34Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Fleming 1968 (Continued)
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Fletcher 1971
Methods This RCT was conducted on the women living in London. Participants were ascribed at
random to 2 treatment groups
Participants Pregnant women booked for antenatal clinic (n = 643).
Interventions Group1: ferrous sulphate 200 mg (n = 322).
Group 2: ferrous sulphate 200 mg + folic acid 5 mg (n = 321)
Outcomes Pre-eclampsia (n = 643), serum folate levels (n = 643).
Notes
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “the subjects were ascribed at ran-
dom to two treatment groups by instruct-
ing each patient to take one tablet daily”
Allocation concealment (selection bias) Unclear risk The methods used for allocation conceal-
ment was not stated in the text
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk The methods used for blinding was not
stated in the text.
Incomplete outcome data (attrition bias)
All outcomes
Unclear risk Number of exclusions and attritions (along
with their reasons) were not reported
Selective reporting (reporting bias) Unclear risk The study appears to be free of selective
reporting.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
35Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Giles 1971
Methods Double-blind controlled trial conducted on patients coming for their antenatal visits at
Royal Women’s Hospital, Melbourne. Women were allotted to the groups based on the
order they were presented. Loss to follow-up was between 10% to 20%
Participants Pregnant women (n = 620).
Interventions Group 1 (folic acid - Tiger) ferrous sulphate 200 mg (n = 308)
Group 2 (folic acid - Lion) folic acid 5 mg (n = 312).
Outcomes Low pre-delivery anaemia (n = 620), birthweight (n = 620), neonatal deaths (n = 620)
Notes
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
High risk Quote: “members of each group were num-
bered consequently in the order in which
they presented”
Comment: probably not done.
Allocation concealment (selection bias) Low risk Quote: “the pharmacist, after consulting a
list of random numbers, dispensed either
folic acid-tiger or folic acid-lion from the
two large stock bottles. these tablets looked
identical, and the dispensing pharmacist
did not know which was the placebo”
Comment: probably done.
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “a double-blind control trial”.
Comment: probably done.
Incomplete outcome data (attrition bias)
All outcomes
Low risk Exclusion data with their reasons were
not reported in the study. Attrition (15%)
along with reasons were reported
Selective reporting (reporting bias) Unclear risk The study appears to be free of selective
reporting.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
36Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Harrison 1985
Methods Double-blind study. The identity of the tables was not known to researcher before the
analysis of the study data and women were randomised to 1 of the 5 groups. Conducted
in Nigeria
Participants Pregnant women of 8 to 24 weeks of pregnancy (n = 69).
Interventions Group A: placebo only (n = 10).
Group B: single dose of chloroquine 600 mg and followed by prognamil 100 mg (n =
18)
Group C: ferrous sulphate 60 mg (n = 12).
Group D: folic acid 1 mg (n = 10).
Group E: ferrous sulphate 60 mg + folic acid 1 mg (n = 9).
Outcomes Red cell folate (µg/L) levels, serum folate levels (n = 69).
Notes For this review group E was compared with group A.
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “women were randomised in dif-
ferent treatment groups”
Allocation concealment (selection bias) Unclear risk The methods used for allocation conceal-
ment was not given in the text
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “the medication was double blind,
the identity if the tablets not being known
to the researchers before the analysis of the
data”
Incomplete outcome data (attrition bias)
All outcomes
Low risk Exclusion and attrition were mentioned to-
gether (70%) along with their reasons
Selective reporting (reporting bias) Low risk The study has mentioned data on all out-
come measures mentioned as objectives
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
37Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Hibbard 1969a
Methods This was a triple-blind study conducted in Mill Road, maternity hospital, Liverpool,
UK. The patients were divided into three groups
Participants Pregnant women (before 20 weeks) with defective folate metabolism and excessive
FIGLU excretion or low serum folate level (< 2 ng/mL) were admitted in the trial (n =
69)
Interventions Treatment groups were daily folic acid 500 µg (n = 27), 0.5 mg folic acid (n = 26), and
placebo (n = 26)
Outcomes Serum folate levels and severe anaemia.
Notes Each group received 60 elemental iron within the trial medicine
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
Unclear risk Quote: “Patients were divided into three
groups”
Allocation concealment (selection bias) Unclear risk Quote“ patients were allocated in consecu-
tive numbers” ; “code wasnot known whilst
the trial was in progress”
Comment: Not enough information to
permit judgement.
Blinding (performance bias and detection
bias)
All outcomes
Low risk Quote: “...gelatin coated capsule of identi-
cal appearance...”
Incomplete outcome data (attrition bias)
All outcomes
Low risk Approximately 19% were lost to follow-up
and folate levels were also checked in the
final non-attendees
Selective reporting (reporting bias) Low risk The study has reported data on outcome
measures mentioned as objectives
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
38Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Iyengar 1975
Methods This RCT was conducted in Niloufer Hospital, Hyderabad (India). Women were alter-
natively assigned to treatment groups. Groups were matched on parity and height. The
women were followed at monthly intervals until 32 weeks of gestation, once every 2
weeks until 36 weeks, and at weekly intervals thereafter until delivery
Participants Pregnant women between 20 and 28 weeks of gestation (n = 288)
Interventions Group 1: no supplement (n = 52), Group 1: iron 60 mg (n = 96), Group 2: iron 60 mg
+ folic acid 500 µg (n = 134)
Outcomes Birthweight (n = 230).
Notes Pregant women belonging to low income less than Rs. 3000/- per month
Risk of bias
Bias Authors’ judgement Support for judgement
Random sequence generation (selection
bias)
High risk Quote: “alternate subjects received either
of therapy”.
Comment: probably not done.
Allocation concealment (selection bias) Unclear risk Insufficient information to permit judge-
ment regarding allocation concealment
Blinding (performance bias and detection
bias)
All outcomes
Unclear risk Insufficient information to permit judge-
ment regarding blinding
Incomplete outcome data (attrition bias)
All outcomes
Low risk Exclusion data with their reasons were not
reported in the study. Attrition (> 20%)
along with reasons were reported
Selective reporting (reporting bias) Low risk Study seems to be free from selective re-
porting.
Other bias Unclear risk No other bias identified but insufficient in-
formation available to fully assess this ’Risk
of bias’ domain
Lira 1989
Methods This is a RCT in which all pregnant women attending the outpatient obstetrics clinic at
the Catholic University’s Clinical Hospital (Chile)
Participants Women with less than 16 weeks of pregnancy were selected (n = 153)
39Folic acid supplementation during pregnancy for maternal health and pregnancy outcomes (Review)
Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.