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Anemia

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Obesity in childbearing women leads to pregnancy-related complications such as gestational diabetes mellitus, pregnancy-associated hypertensive disorders, and macrosomia. Weight loss helps reduce these complications. Studies show bariatric surgery reduces obesity-related complications during and after pregnancy. However, bariatric surgery might be associated with adverse outcomes, such as low birth weight and small-for-gestational-age infants. In addition, several studies suggest pregnancy occurring less than a year post-bariatric surgery adversely affects pregnancy outcomes and causes micronutrients deficiency since the dramatic weight loss occurs in the first year. These adverse outcomes may lead to nutritional malabsorption, such as anemia and low vitamin B12 and folic acid levels. The review aims to overview obesity-related complications during pregnancy and the benefits and risks of bariatric surgery on pregnancy outcomes and maternal nutrition status. Graphical abstract
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Background The definition for anemia in pregnancy is outdated, derived from Scandinavian studies in the 1970’s to 1980’s. To identity women at risk of blood transfusion, a common cause of Severe Maternal Morbidity, a standard definition of anemia in pregnancy in a modern, healthy United States cohort is needed. Objective To define anemia in pregnancy in a United States population including a large county vs. private hospital population using uncomplicated patients. Materials and methods Inclusion criteria were healthy women with the first prenatal visit before 20 weeks. Exclusion criteria included preterm birth, preeclampsia, hypertension, diabetes, short interval pregnancy (<18 months), multiple gestation, abruption, and fetal demise. All women had iron fortification (Ferrous sulfate 325 mg daily) recommended. The presentation to care and pre-delivery hematocrits were obtained, and the percentiles determined. A total of 2000 patients were included, 1000 from the public county hospital and 1000 from the private hospital. Each cohort had 250 patients in each 2011, 2013, 2015, and 2018. The cohorts were compared for differences in the fifth percentile for each antepartum epoch. Student’s t-test and chi-squared statistical tests were used for analysis, p-value of ≤0.05 was considered significant. Results In the public and private populations, 777 and 785 women presented in the first trimester while 223 and 215 presented in the second. The women at the private hospital were more likely to be older, Caucasian race, nulliparous, and present earlier to care. The fifth percentile was compared between the women in the private and public hospitals and were clinically indistinguishable. When combining the cohorts, the fifth percentile for hemoglobin/hematocrit was 11 g/dL/32.8% in the first trimester, 10.3 g/dL/30.6% in the second trimester, and 10.0 g/dL/30.2% pre-delivery. Conclusions Fifth percentile determinations were made from a combined cohort of normal, uncomplicated pregnancies to define anemia in pregnancy. Comparison of two different cohorts confirms that the same definition for anemia is appropriate regardless of demographics or patient mix.
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A normal pregnancy consumes 500–800 mg of iron from the mother. Premenopausal women have a high incidence of marginal iron stores or iron deficiency (ID), with or without anemia, particularly in the less developed world. Although pregnancy is associated with a “physiologic” anemia largely related to maternal volume expansion; it is paradoxically associated with an increase in erythrocyte production and erythrocyte mass/kg. ID is a limiting factor for this erythrocyte mass expansion and can contribute to adverse pregnancy outcomes. This review summarizes erythrocyte and iron balance observed in pregnancy; its implications and impact on mother and child; and provides an overview of approaches to the recognition of ID in pregnancy and its management, including clinically relevant questions for further investigation.
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Objective: To estimate the incidence of anemia in pregnancy and compare the maternal and perinatal outcomes of women with and without anemia. Methods: We conducted a population-based retrospective cohort study on all pregnant women in British Columbia who had a live birth or stillbirth at or after 20 weeks of gestation between 2004 and 2016. Women were diagnosed with anemia based on two criteria: third-trimester hemoglobin value or a delivery admission diagnosis of anemia (made before delivery). Anemia was categorized into no anemia (hemoglobin 11 g/dL or greater), mild (9-10.9 g/dL), moderate (7-8.9 g/dL), severe (less than 7 g/dL), or anemia of unspecified severity (with diagnosis made before delivery). Logistic regression was used to estimate adjusted odds ratios (aOR) and 95% CIs expressing the association between anemia and maternal and perinatal outcomes. Results: Of 515,270 women in the study population, 65,906 (12.8%) had anemia: 11.8%, 0.43%, and 0.02% had mild, moderate, and severe anemia, respectively, and 0.58% had anemia of unspecified severity. Anemic women had longer hospitalization duration and more antenatal admissions, and rates of preeclampsia, placenta previa and cesarean delivery were higher among women with anemia. The intrapartum-postpartum blood transfusion rate was 5.1 per 1,000 among women without anemia, and higher among women with anemia (aOR 2.45, 95% CI 1.74-3.45 for mild anemia; 21.3, 95% CI 12.2-37.3 for moderate anemia; not analyzable for severe anemia; and 48.3, 95% CI 6.60-353.9 for anemia of unspecified severity). Anemia was associated with preterm birth (mild anemia, aOR 1.09, 95% CI 1.05-1.12; moderate anemia, aOR 2.26, 95% CI 2.02-2.54; anemia of unspecified severity, aOR 2.27, 95% CI 2.06-2.50), small-for-gestational-age live birth, low 5-minute Apgar score, neonatal death, and perinatal death. Conclusion: Maternal anemia in pregnancy represents a common and potentially reversible risk factor associated with antepartum, intrapartum, and postpartum maternal morbidity and perinatal morbidity and mortality.
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INTRODUCTION: As many as 17% of Canadian women suffer from iron deficiency anemia (IDA) in pregnancy. Treatment options include oral ferrous salts, haem iron, intravenous (IV) iron and blood transfusions. Trade-offs pregnant women are willing to make to alleviate symptoms of IDA have not been determined. This study elicits preferences of pregnant women for health-states arising from IDA and the use of various treatment options. METHODS: A cross-sectional study was conducted on pregnant women with and without IDA. Participants were presented with five vignettes representing maternal health-states arising from IDA in pregnancy. They were asked to rank these states and assign them values on a visual analogue scale, by the standard gamble, and by time trade-off methods. Utility values (preferences) of women with and without IDA, obtained from these methods were presented on a scale of 0-100 where 0 represented death and 100 represented perfect health. RESULTS: 60 pregnant women (30 with IDA and 30 without) completed the interviews. With all three methods, utility values were lowest for blood transfusion and highest for oral iron. Regardless of the evaluation method, there was no difference in utility values for treatment with oral ferrous salts vs. haem iron or between women with or without IDA. CONCLUSION: Women acknowledge that symptoms of IDA in pregnancy reduce quality of life. Despite side effects and frequency of administration, oral iron is preferred over IV iron and blood transfusion. Confirmation of these findings in larger studies would directly inform clinical practice and research.
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Total body iron calculated from serum ferritin and soluble transferrin receptor concentrations allows for the evaluation of the full range of iron status. We described the distribution of total body iron and the prevalence of iron deficiency (ID) on the basis of total body iron in US pregnant women. We examined data from the National Health and Nutrition Examination Survey (NHANES) in 1999-2006 for 1171 pregnant women. ID prevalence (±SE) in US pregnant women, which was defined as total body iron <0 mg/kg, was 18.0 ± 1.4%. Pregnant women in the first trimester had a higher mean total body iron than did pregnant women in the second or third trimesters. ID prevalence in pregnant women increased significantly with each trimester (6.9 ± 2.2%, 14.3 ± 2.1%, and 29.5 ± 2.7% in the first, second, and third trimesters, respectively). Pregnant women with parity ≥2 had the lowest mean total body iron and the highest prevalence of ID compared with values for pregnant women with parity of 0 or 1. The ID prevalence in non-Hispanic white pregnant women was significantly lower than in Mexican American or non-Hispanic black pregnant women. The mean total body iron and the prevalence of ID did not differ by educational level or by family income. To our knowledge, these are the first data on total body iron distributions for a representative sample of US pregnant women. Low total body iron is more prevalent in pregnant women in the second or third trimesters, in Mexican American pregnant women, in non-Hispanic black pregnant women, and in women with parity ≥2.
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The association between anemia during pregnancy and spontaneous preterm birth was studied with a two-stage case-control design in a large, multiethnic cohort. Results of all hematologic measurements were abstracted from the prenatal and delivery records of 1706 of the 26,901 women in the cohort. Among women delivered of infants at term, mean hematocrit value was low during the early phase of the second trimester, stable until near term, then reached a maximum at 40 weeks' gestation. The mean hematocrit value of black women was consistently lower than that of Asian, Mexican, and white women. Anemia (hematocrit value less than the tenth percentile for ethnic group and duration of pregnancy) at any time during the second trimester was positively associated with subsequent spontaneous preterm birth (odds ratio, 1.9; 95% confidence interval, 1.3 to 2.8). Compared with white women, the odds ratios for preterm birth were 2.0 (95% confidence interval, 1.6 to 2.4) for black, 1.2 (95% confidence interval, 0.9 to 1.6) for Asian, and 1.2 (95% confidence interval, 1.0 to 1.5) for Mexican women. Adjustment for second-trimester anemia had minimal influence on the odds ratios. We conclude that anemia during the second trimester was associated with preterm birth. However, it does not account for the large ethnic differences in preterm birth.
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In a hospital-based cohort of 8903 black and white women, we investigated medical and socioeconomic risk factors that may explain the known increase in premature births among black women. Among the medical conditions examined, only the maternal hematocrit level (or some related factor) explained a substantial proportion (60 percent) of the increased rate of premature births to black women. Four economic, demographic, and behavioral predictors of prematurity were also examined: age less than 20 years, single marital status, receiving welfare support, and not having graduated from high school. The number of these socioeconomic risk factors occurring in a woman was strongly predictive of premature birth of her infant, regardless of the particular risk factors present. The presence of any one factor was associated with a moderate increase in the risk of prematurity (7.0 percent as compared with 4.6 percent with no risk factors present); the presence of two or more characteristics was associated with a much higher risk (11.2 percent). When the number of these four risk factors pertaining to an individual woman was taken into account, race was no longer a significant predictor of premature birth (odds ratio, 1.22; 95 percent confidence interval, 0.94 to 1.59). When both the maternal hematocrit level and the number of the four socioeconomic risk factors were taken into account, essentially all of the racial variation in prematurity was explained, with the odds ratio for prematurity among blacks being 1.03 (95 percent confidence interval, 0.79 to 1.35). We conclude that the racial difference in the rate of premature birth is attributable to specific medical and socioeconomic characteristics.
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To examine the association of maternal hemoglobin during pregnancy with preterm birth and small for gestational age (SGA). We performed a retrospective cohort analysis of hemoglobin and birth outcome among 173,031 pregnant women who attended publicly funded health programs in ten states and delivered a liveborn infant at 26-42 weeks' gestation. We defined preterm as less than 37 weeks' gestation and SGA as less than the tenth percentile of a US fetal growth reference. Risk of preterm birth was increased in women with low hemoglobin level in the first and second trimester. The odds ratio (OR) for preterm birth with moderate-to-severe anemia during the first trimester (more than three standard deviations [SD] below reference median hemoglobin, equivalent to less than 95 g/L at 12 weeks' gestation) was 1.68 (95% confidence interval [CI] 1.29, 2. 21). Anemia was not associated with SGA. High hemoglobin level during the first and second trimester was associated with SGA but not preterm birth. The ORs for SGA in women with very high hemoglobin level during the first and second trimester (more than three SDs above reference median hemoglobin, equivalent to greater than 149 g/L at 12 weeks' gestation and greater than 144 g/L at 18 weeks') were 1.27 (95% CI 1.02, 1.58) and 1.79 (95% CI 1.49, 2.15), respectively. These data highlight the importance of considering anemia and high hemoglobin level as indicators for adverse pregnancy outcome. An elevated hemoglobin level (greater than 144 g/L) is an indicator for possible pregnancy complications associated with poor plasma volume expansion, and should not be mistaken for good iron status.
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With race-based definitions of antepartum anemia, Black women are at significant increased odds of delivery admission hemoglobin<11g/dL than non-Black women with the same antepartum hemoglobin.
Article
Importance: Globally, more than 125 million women each year are at risk of malaria during pregnancy. Endemic regions carry the greatest burden; however, with globalization, providers in nonendemic regions are encountering increasing numbers of women exposed to or infected with malaria. Objectives: The aim of this article is to provide obstetric providers in nonendemic areas with updated information on malaria infection in pregnancy focusing on pregnancy management and malaria prevention and treatment. Evidence acquisition: This article is based on review of the most recent peer-reviewed articles and guidelines from the Centers for Disease Control and Prevention and the World Health Organization. Findings: Malaria infection in pregnancy causes maternal anemia, low birth weight, preterm birth, stillbirth, and miscarriages through placental malaria and severe infections. Pregnant women traveling to malaria-endemic areas should be advised against travel. If travel must occur, they should be provided with region-specific chemoprophylaxis and given methods for preventing infection. In the event that a pregnant patient has an acute malarial infection, prompt evaluation is needed to determine whether there are severe features. Medications for uncomplicated or severe malaria infection should be started as soon as the diagnosis is made. Conclusions and relevance: Malaria in pregnancy causes significant perinatal complications. Obstetric providers should be aware of the impact and how to prevent and treat malaria infection during pregnancy. Malaria infection should be suspected in women with concerning symptoms and recent travel to endemic areas. Providers should know the management of uncomplicated and severe malarial infection in pregnancy.
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Objective: To perform a systematic review of randomized trials comparing oral vs intravenous (IV) iron therapy to treat postpartum anemia. Data sources: Data sources were as follows: PubMed (1972-2017); Cochrane Central Register of Controlled Trials, CENTRAL (1972-2017); CINAHL (1972-2017); Web of Science; Excerpta Medica Database, and EMBASE (1972-2017). Study eligibility criteria: We included randomized trials comparing oral vs IV iron monotherapy to treat postpartum anemia (classified as a hemoglobin <12 g/dL). Study appraisal and synthesis methods: Study quality was assessed with the Cochrane risk of bias assessment tool. The primary outcome was hemoglobin concentration at 6 weeks postpartum. Secondary outcomes included hemoglobin concentration at 1-5 weeks postpartum, ferritin concentration at 1-6 weeks postpartum, and maternal adverse outcomes. For meta-analysis, mean differences and odds ratios using a random effects model were calculated. Risk of heterogeneity was reported as I2. Results: A total of 15 randomized trials met our inclusion criteria (n = 1001 and 1 181 women receiving oral iron and IV iron, respectively); 4 studies reported data for our primary outcome. We observed higher postpartum week 6 hemoglobin concentrations in the IV iron group compared to the oral iron group (mean difference, 0.9 g/dL; 95% confidence interval (CI), 0.4-1.3; P = .0003). Compared to oral iron, women receiving IV iron had higher hemoglobin concentrations at postpartum weeks 1, 2, and 3; higher ferritin concentrations at postpartum weeks 1, 2, 4, and 6; an increased likelihood of skin flushing (odds ratio [OR], 6.95; 95% CI, 1.56-31.03; P = .01; I2 = 0%); and a decreased likelihood of constipation (OR, 0.08; 95% CI, 0.03-0.21; P < .00001, I2 = 27%) and dyspepsia (OR, 0.07; 95% confidence interval, 0.01-0.42; P = .004; I2 = 0%). The reported event rate for anaphylaxis among women receiving IV iron was 0.6%. Conclusion: In this systematic review, among women with postpartum anemia, hemoglobin concentrations at 6 weeks postpartum were almost 1 g/dL higher in women who received IV iron compared to oral iron. The safety profile of IV iron was also reassuring. Given the weaker hemoglobin response and higher risk of gastrointestinal side effects with oral iron use, our findings suggest that IV iron be considered as a viable treatment option for postpartum iron deficiency anemia.
Article
INTRODUCTION According to the World Health Organization, anemia affects 42% of pregnancies globally. Oral (PO) iron is standard of care, but poor absorption limits efficacy. Thus, intravenous (IV) iron has been compared to PO iron in randomized control trials (RCTs). We performed an RCT meta-analysis to assess the benefits of IV iron in pregnancy. METHODS This meta-analysis was performed according to Meta-analysis of Observational studies in Epidemiology (MOOSE) guidelines. We searched PUBMED, clinicaltrials.gov, Google scholar, and Cochrane library. 297 articles were reviewed, and after exclusions, 10 RCTs comparing IV to PO iron in pregnancy were included. Studies confirmed iron-deficiency anemia before treatment. Endpoints were: 1) Subjects achieving target hemoglobin; 2) Hemoglobin increase at 4 weeks and; 3) Subjects experiencing adverse effects. Meta-analyses were performed with Stata (College Station, TX), with summary odds ratios by Mantel-Haenszel method and pooled risk difference by Cohen's method. RESULTS Data from 10 RCTs were utilized for pooled meta-analysis. Pregnant women were more likely to achieve target hemoglobin with IV versus PO iron (7 studies), summary OR 2.7 (95% CI 2.0–3.6), P <.001. Hemoglobin levels increased more at 4 weeks with IV iron (8 studies), mean difference 1.2 g/dL (95% CI 1.0–1.3), P <.001. Adverse reactions were lower with IV versus PO iron (10 studies), summary OR 0.54 (95% CI 0.41–0.72), P <.001. CONCLUSION In this RCT meta-analysis, IV iron is superior to oral iron for treatment of iron-deficiency anemia in pregnancy. Women receiving IV iron more often achieve desired hemoglobin targets, faster, with less side effects.
Article
INTRODUCTION Anemia in pregnancy has been associated with increased rates of low birth weight, preterm delivery, and perinatal mortality in several previous studies. Despite these complications, few have investigated the impact of anemia on postpartum women. This postpartum period can be extremely difficult for mothers as 19% of United States women experience postpartum depression (PPD). It is therefore imperative to investigate anemia as a possible physiologic risk factor for PPD. METHODS This retrospective cohort study was conducted by collecting hematocrit and demographic data from medical records of patients meeting all criteria. Patients included were women ≥16 years old who received postpartum care at Women’s Ambulatory Health Services in Hartford, Connecticut from January 2014 to January 2017. Those excluded were patients <16 years old, those on psychiatric medications, those with disease disrupting iron metabolism, tobacco users, patients receiving blood transfusions, or those experiencing neonatal mortality. Records were categorized into anemic and non-anemic. Percentage of Edinburgh Postnatal Depression Scale (EPDS) ≥11 vs <11 were compared using Chi square test. RESULTS 922 women fulfilled study requirements and completed the EPDS questionnaire. 9.2% of study patients screened positively for PPD (EPDS ≥11). 75.2% were anemic antenatally or immediately postpartum. The difference in PPD incidence for those anemic (10.8%) vs non-anemic (4.8%) was statistically different (P=.007). Anemic patients had an increased risk of screening positive for PPD (RR 2.25, 95% CI 1.22-4.16). CONCLUSION Anemia during pregnancy or peripartum is associated with an increased incidence of PPD and thus should be further investigated as a potential risk factor for PPD.
Article
INTRODUCTION A third of women have antepartum anemia, potentially leading to maternal and neonatal morbidity and mortality. Allogenic blood transfusion is often an appropriate treatment. Available evidence suggests antepartum correction may decrease postpartum transfusion volumes. This retrospective cohort study investigated the relationship between anemia at mid-trimester (24-28 weeks or third trimester) and estimated blood loss (EBL) and transfusion at delivery. METHODS All deliveries between January 2014 and March 2015 at our institution were eligible for inclusion. Exclusion criteria included delivery <24 weeks gestational age and unknown mid-trimester hemoglobin. Anemia was defined as hemoglobin RESULTS 1071 patients were included. 473 (44.16%) were anemic at mid-trimester and 36 (3.36%) required postpartum transfusion. Of patients non-anemic at mid-trimester, 7% were anemic at delivery compared to 57% of those who were anemic at mid-trimester (p<0.001). Five (0.84%) non-anemic patients required transfusion compared to 31 (6.55%) anemic patients (p=<0.001). Of transfused patients, EBL was higher in non-anemic compared to anemic patients (mean EBL 2520.00+/-962.81ml vs. 1601.45+/-1464.38ml, p=0.04). Mean transfusion volume did not differ (not anemic 3.60+/-1.67 vs. anemic 2.67+/-2.44, p=0.011). CONCLUSION Patients with anemia at mid-trimester were significantly more likely to be anemic at delivery. These patients had higher rates of postpartum blood transfusion despite lower EBL than non-anemic patients. The trend toward lower transfusion volume for anemic patients suggests that these may be preventable. Treatment of anemia at mid-trimester is essential.
Article
The iron stores of 114 white college women who had never experienced abnormal bleeding nor been pregnant were evaluated using marrow stainable iron and in some instances quantitative phlebotomy. Even though the subjects were somewhat privileged socioeconomically, iron stores were scant to absent in two thirds of them. After being made anemic by repeated phlebotomy, the anemia was corrected at a very slow rate by iron absorbed from their diet. Consequently iron in an effective dose and form should be administered to women who have anemia and iron deficiency or who are hemorrhaging.
Article
Epidemiological studies describe an association between relative size of the placenta at delivery and cardiovascular morbidity and mortality during adult life. Some determinants of placental size, such as maternal anaemia, have been acknowledged, but no plausible mechanism has been advanced to explain the initiation of postnatal disease. Placental villous vascularisation in anaemic women (Hb<90 g/L) was assessed in the first and third trimesters of pregnancy by immunohistochemical identification of villous capillaries and compared with that of gestational age-matched groups of women with normal (Hb>110 g/L; control group) concentrations of haemoglobin, and an intermediate group (Hb 90-110 g/L). Anaemia, especially in the first trimester, was associated with increased numbers of capillaries per villous cross section (mean 11.70 [SE 0.35] vs 4.14 [0.27]) located mainly in the outer third of the stroma beneath the trophoblast (94% [1.15] vs 67% [1.82]) and with increased numbers of villous macrophages and of proliferating MIB-1-positive cells compared with the control group. Maternal anaemia in early pregnancy seems to influence the pattern of placental vascularisation. Such changes might alter placental vascular impedance during early fetal life, thereby exerting important effects on cardiovascular development.
Article
This study's objectives were to determine the national prevalence of anemia in pregnancy (AIP) in the United States, compare racial differences in the prevalence, compare the AIP risk factor profiles between non-Hispanic whites and non-Hispanic blacks, and to analyze the associations between AIP and some maternal and fetal/neonatal complications between whites and blacks. The data used were from the United States natality data files (1995 through 2000), which included 23,654,695 live births. All mothers diagnosed with AIP, defined as hemoglobin-concentration < 10 g/dl, were included. The cohorts were analyzed in two groups. The "whole group" (WG) comprised all women in the data set who had anemia status reported. The "low-risk group" (LRG) comprised women with low-risk factors for AIP. Race was determined by mothers' skin colors and racial self-identifications. Logistic regression was used to explore associations between race and AIP while controlling for other covariates. The national prevalence of AIP among the general population was 21.55/1,000 among the WG and 11.51/1,000 among the LRG. Among the WG, the prevalence of AIP was two times higher among non-Hispanic blacks (35.38/1,000) than among non-Hispanic whites (18.02/1,000). Among the LRG, the prevalence was 1.94 times higher among non-Hispanic blacks (20.44/1,000) than among non-Hispanic whites (10.63/1,000). The other risk factor profiles for AIP were similar among the races. Many serious maternal and fetal/neonatal complications occurred more frequently among anemic patients when compared with non-anemic patients. The results of this study showed that black race was significantly associated with higher risk of AIP. The other risk factor profiles of AIP were significantly similar between whites and blacks. This study also confirmed that AIP was significantly associated with some serious maternal and fetal/neonatal complications. The findings of this study indicate that race is an important risk factor of AIP.
Article
It has been suggested that routine intake of supplements containing iron or combination of iron and folic acid during pregnancy improves maternal health and pregnancy outcomes. To assess the efficacy, effectiveness and safety of routine antenatal daily or intermittent iron supplementation with or without folic acid during pregnancy on the health of mothers and newborns. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (June 2005). Additionally, we contacted relevant organizations for the identification of ongoing and unpublished studies. All randomised or quasi-randomised trials evaluating the effect of routine supplementation with iron or combination of iron and folic acid during pregnancy. We assessed trials for methodological quality using the standard Cochrane criteria. Two authors independently assessed the trials for inclusion and one author extracted data. We collected information on randomisation method, allocation concealment, blinding and loss to follow up. The primary outcomes included maternal and infant clinical and laboratory outcomes. Forty trials, involving 12706 women, were included in the review. Overall, the results showed significant heterogeneity across most prespecified outcomes. Heterogeneity could not be explained by standard sensitivity analyses including quality assessment; therefore, all results were analysed assuming random-effects. Very limited information related to clinical maternal and infant outcomes was available in the included trials. The data suggest that daily antenatal iron supplementation increases haemoglobin levels in maternal blood both antenatally and postnatally. It is difficult to quantify this increase due to significant heterogeneity between the studies. Women who receive daily antenatal iron supplementation are less likely to have iron deficiency and iron-deficiency anaemia at term as defined by current cut-off values. Side-effects and haemoconcentration are more common in women who receive daily iron supplementation. No differences were evident between daily and weekly supplementation with regards to gestational anaemia; haemoconcentration during pregnancy appears less frequent with the weekly regimen. The clinical significance of hemoconcentration defined as haemoglobin greater than 130 g/L remains uncertain. Further studies are needed to assess the effects of routine antenatal supplementation with iron or a combination of iron and folic acid on clinically important maternal and infant outcomes.