Daily iron during pregnancy improves birth weight

BMJ 2013; 346 doi: (Published 21 June 2013) Cite this as: BMJ 2013;346:f3997
  1. Jacqui Wise
  1. 1London

A daily dose of iron during pregnancy reduces anaemia and is associated with a significant increase in birth weight and a reduction in risk of low birth weight, a systematic review and meta-analysis has shown.1

The researchers, from the Harvard School of Public Health, found a dose-response relation: for every 10 mg increase in iron dose each day (up to 66 mg a day) the risk of maternal anaemia was 12% lower, birth weight was 15 g higher, and the risk of low birth weight was 3% lower.

The analysis, published on, looked at 48 randomised trials (17 793 women) and 44 cohort studies (1 851 682 women). Use of iron supplementation increased maternal mean haemoglobin concentration by 4.59 g/L (95% confidence interval 3.72 to 5.46 g/L) when compared with controls and significantly reduced the risk of anaemia, iron deficiency, iron deficiency anaemia, and low birth weight.

There was no reduction in the risk of preterm birth as a result of iron use, but an analysis of cohort studies showed a significantly higher risk of low birth weight and preterm birth if the mother had anaemia in the first or second trimester of pregnancy.

Iron deficiency is the most widespread nutritional deficiency in the world and is the commonest cause of anaemia during pregnancy, particularly in low and middle income countries. The World Health Organization recommends a dose of 60 mg a day for pregnant women.

The authors wrote, “Our findings suggest that use of iron in women during pregnancy may be used as a preventative strategy to improve maternal haematological status and birth weight.” They call for an evaluation of current antenatal care programmes and an examination of ways to deliver extra iron, such as through food fortification.

Previous studies have indicated an association between prenatal anaemia and risk of premature birth, but evidence on other birth outcomes has been inconclusive. The effect of prenatal iron on adverse birth outcomes has also been unclear. A Cochrane review of prenatal iron supplementation in 2009 found no evidence of a reduction in risk of low birth weight and preterm birth.2


Cite this as: BMJ 2013;346:f3997