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.

Authors' conclusions: 

We found no conclusive evidence of benefit of folic acid supplementation during pregnancy on pregnancy outcomes.

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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 strategy: 

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).

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.

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).

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