Walsh et al. BMC Pregnancy and Childbirth 2010, 10:16
A randomised control trial of low glycaemic index
carbohydrate diet versus no dietary intervention in
the prevention of recurrence of macrosomia
© 2010 Walsh et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Jennifer Walsh*, Rhona Mahony, Michael Foley and Fionnuala Mc Auliffe
Background: Maternal weight and maternal weight gain during pregnancy exert a significant influence on infant birth
weight and the incidence of macrosomia. Fetal macrosomia is associated with an increase in both adverse obstetric
and neonatal outcome, and also confers a future risk of childhood obesity. Studies have shown that a low glycaemic
diet is associated with lower birth weights, however these studies have been small and not randomised [1,2]. Fetal
macrosomia recurs in a second pregnancy in one third of women, and maternal weight influences this recurrence risk
Methods/Design: We propose a randomised control trial of low glycaemic index carbohydrate diet vs. no dietary
intervention in the prevention of recurrence of fetal macrosomia.
Secundigravid women whose first baby was macrosomic, defined as a birth weight greater than 4000 g will be
recruited at their first antenatal visit.
Patients will be randomised into two arms, a control arm which will receive no dietary intervention and a diet arm
which will be commenced on a low glycaemic index diet.
The primary outcome measure will be the mean birth weight centiles and ponderal indices in each group.
Discussion: Altering the source of maternal dietary carbohydrate may prove to be valuable in the management of
pregnancies where there has been a history of fetal macrosomia. Fetal macrosomia recurs in a second pregnancy in
one third of women. This randomised control trial will investigate whether or not a low glycaemic index diet can affect
this recurrence risk.
Current Controlled Trials Registration Number: ISRCTN54392969
Over one billion adults in the world are now overweight,
with more than 300 million clinically obese . In the
United States, the prevalence of obesity in women aged
20 - 39 years rose from 9% in 1960 - 1962 to 28% in 1999 -
2000 . In Ireland, mothers are now 10 kg heavier in
pregnancy than 20 years ago . Increased maternal body
mass index (BMI) confers an elevated risk of delivering a
heavier infant, while increasing maternal weight gain
during pregnancy has been shown to be independently
related to increasing infant birth weight[6,7]. The
increasing birth weight seen in Ireland in recent decades
is a potential cause for concern, not only because of its
association with increased instrumental delivery and
perineal trauma, but also because of the association
between birth weight and childhood obesity.
The westernized diet rich in carbohydrates is thought
to contribute to the rates of obesity. Carbohydrate
sources are classified according to their induced glucose
response which is referred to as glycaemic index . The
glycaemic index is defined as the incremental area under
the blood glucose curve (AUC) after ingestion of 50
grams of a test food, expressed as a percentage of the
AUC of an equal amount of a reference food (usually glu-
cose or white bread). Low glycaemic index foods
* Correspondence: email@example.com
1 Department of Obstetrics and Gynaecology, University College Dublin
National Maternity Hospital, Dublin, Ireland
Full list of author information is available at the end of the article
Walsh et al. BMC Pregnancy and Childbirth 2010, 10:16
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induce a low glucose response e.g. whole grain breads,
cereals, nuts, dairy foods and high glycaemic index foods
induce a high glucose response e.g. processed grains such
as flour and bread, snack foods, desserts, soft drinks.
It has been shown that a low glycaemic diet blunts the
mid and late pregnancy increase in insulin resistance typ-
ically seen in westernized societies . These studies
suggest that the loss of insulin sensitivity, which is typical
of Western women in the third trimester of pregnancy
and is considered to be physiological, may be diet-
Altering the source of maternal dietary carbohydrate
may prove to be valuable in the management of pregnan-
cies where there has been a history of fetal macrosomia.
Fetal macrosomia recurs in a second pregnancy in one
third of women, and maternal weight influences this
recurrence risk. We propose to randomise secundi-
gravid women whose first baby was macrosomic (birth
weight >4.0 Kg) to receive either no dietary intervention
or to be commenced on a low glycaemic index diet during
second pregnancy. The primary endpoint of this study is
the differences in birth weight between the 2 groups.
We will conduct a randomised control trial of low glycae-
mic index diet versus no intervention in prevention of
recurrence of macrosomia.
The primary outcome measure will be the mean birth
The secondary outcome measure will be the difference
between the two groups in maternal weight gain in preg-
The study will be carried out in the National Maternity
Secundigravid women whose first baby was mac-
rosomic, defined as a birth weight greater than 4000 g will
be recruited at first booking visit.
Subjects will be excluded if they have diabetes, other
medical disorders and those with poor previous preg-
Patients will be randomised into two groups: a control
arm which will receive no dietary intervention and a diet
arm which will be commenced on a low glycaemic index
diet from 14 weeks gestation to delivery under dietetic
Randomisation will be achieved using computer gener-
ated allocations in a ratio of 1:1 contained in sealed
Women choosing to enter the study will give written
informed consent. Data will be collected on those women
approached for study participation and who declined to
ensure those participating are representative of this entire
Each patient in the diet arm will receive an individual-
ised diet which will be energy matched as appropriate to a
patients average caloric intake with the aim of reducing
glycaemic load and glycaemic excursions. This diet is
eucaloric and is not designed to promote weight loss. In
the diet arm each patient will have one dietetic session, in
groups of 4-6 at 12-16 weeks' gestation, with the aim of
commencing the diet at 16 week's gestation. At booking
visit all patients will have their height and weight
recorded and their BMI will be calculated (Maternal
weight Kg/Height in metres2). Additional demographic
data including smoking history, SEG and paternal weight
and height will be recorded.
In addition to routine care the following additional tests
will be performed.
1. Food frequency questionnaire at 12, 28 weeks' ges-
tation and 3 months post partum. Average weekly
exercise will also be recorded as part of this question-
naire. The food questionnaire will use questions from
section I of the 'Slan national health and lifestyle sur-
vey' 2002. This has been validated in an Irish popula-
tion. At 3 months postpartum the questionnaire will
assess compliance to the low glycaemic index diet fol-
lowing pregnancy. Information at 12 weeks will allow
baseline information to be obtained. Assessment at 28
week's gestation will assess compliance to the diet in
the intervention arm.
2. At each visit maternal weight will be recorded: 12,
20, 28, 34, 36, 38, 40 weeks' gestation.
3. At 12 weeks' fasting blood glucose, mid upper arm
circumference and body mass index will be taken.
4. Glucose challenge test at 28 weeks. It is important
to determine the presence of gestational diabetes in
this group. If gestational diabetes is present care will
continue in the multidisciplinary diabetic clinic.
5. Fetal growth ultrasound at 34 weeks. Fetal biome-
try including anterior abdominal wall thickness will
be measured to ensure normal fetal growth velocity
and for comparison to the birth weight.
6. Neonatal anthropometry. At delivery, infant birth
weight, infant length and head circumference will be
recorded in all cases as is current routine practice.
The birth weight centile and ponderal index will be
Power analysis was performed by Professor Helen Col-
houn. The primary outcome measure is the difference in
the birth weight post intervention versus control women,
adjusted for birth weight of the first child, i.e. the differ-
ence between intervention and control groups in the
change in gender and gestational age adjusted birth
weight achieved. The sample size required depends on a
significance level set at conventional level of 5% and
power set at conventional level of 90%. To detect a 0.25
SD difference in birth weight- this is equivalent to a 102 g
Walsh et al. BMC Pregnancy and Childbirth 2010, 10:16 Download full-text
Page 3 of 3
difference in the birth weights achieved in control and
intervention groups one would need 360 women in each
group. A sample size of 360 women in each group will
have 90% power to detect a difference of at least 100 g in
birth weight between control and intervention groups.
Thus 720 women will be randomised to 'no intervention'
or to 'low glycaemic index diet. Based on 2004 figures at
NMH 2700 women annually are secundigravid, with an
estimated 20% with a previous baby > 4 kg gives 540
annually available for participation. An estimated 20% (n
= 108) will either be ineligible for the study due to inade-
quate English (14%), history of medical disorder or poor
obstetric history (2%), multiple pregnancy (2%), gesta-
tional diabetes (2%) leaving 432 women suitable for
recruitment. Assuming a 70% participation rate we esti-
mate that up to 300 women annually will be recruited.
This study had received approval from the ethics com-
mittee of the National Maternity Hospital (June 2006).
The purpose of this randomised trial is to assess the
impact of a maternal eucaloric low glycaemic index diet
on birth weight. We will also assess its impact on mater-
nal weight gain in pregnancy. In addition this study will
examine the effect of this diet on maternal metabolism,
fetal insulin, fetal growth factors and placental develop-
ment. The results will increase our understanding of the
inter-relation between maternal nutrition and pregnancy
outcome. If the findings show a beneficial effect of this
eucaloric low glycaemic index diet on birth weight and on
maternal weight gain, then it may applicable generally to
women with increased body mass index, or those at risk
of macrosomia. Prevention of macrosomia at birth will
help reduce the incidence of childhood and subsequent
adult obesity . The outcome of this study will delin-
eate the relationship between maternal nutrition, fetal
programming and infant birth weight, and could have a
significant impact on the application of public health
nutrition policies on maternal and fetal nutrition.
The authors declare that they have no competing interests.
JW wrote the manuscript, coordinates the day to day running of the study and
will analyse and interpret the findings. RM and MF contributed to the design
and conduct of the study and contributed to the writing of the manuscript.
FMcA conceived and designed the study and contributed to the writing of the
manuscript. All authors read and approved the final manuscript.
Health Research Board, Ireland
Department of Obstetrics and Gynaecology, University College Dublin
National Maternity Hospital, Dublin, Ireland
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The pre-publication history for this paper can be accessed here:
Cite this article as: Walsh et al., A randomised control trial of low glycaemic
index carbohydrate diet versus no dietary intervention in the prevention of
recurrence of macrosomia BMC Pregnancy and Childbirth 2010, 10:16
Received: 16 November 2009 Accepted: 23 April 2010
Published: 23 April 2010
This article is available from: http://www.biomedcentral.com/1471-2393/10/16 © 2010 Walsh et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
BMC Pregnancy and Childbirth 2010, 10:16