Iron and folate supplementation in pregnancy

Routine iron and folate supplementation during the latter half of pregnancy helps to maintain serum ferritin above 10 µg/l and serum folate above 2.5-3 µg/l, and helps to reduce substantially the proportion of women with haemoglobin (Hb) levels below 10-10.5 g/dl in late pregnancy. The available studies provide little objective and statistically valid information on the effect of routine iron and folate supplementation on maternal and fetal clinical outcomes when parameters such as pregnancy-induced hypertension, urinary tract infection, antepartum haemorrhage, preterm delivery, low birth weight, admission to a neonatal unit and incidence of stillbirth/neonatal death, are assessed. There does, however, appear to be a reduction in the rate of caesarean section. The author of the review cautions the reader regarding drawing conclusions based on single studies.

No mention is made in the review of the association between low serum folic acid levels prior to or around the time of conception and the risk of neural tube defects and of the risk of entering the next pregnancy deficient in folate (after a previous pregnancy followed by a period of lactation). It is understood, however, that this topic is reviewed separately (1). This may be particularly relevant in the areas where sources of folic acid (green/yellow leafy vegetables) are in short supply or where there is a high incidence of neural tube defect(2,3).

A total of eight studies were included in the review. The overall statistical validity and relevance of the findings of these studies are questionable in view of the small number of studies involved. However, for certain parameters (haematological, biochemical, pregnancy-associated hypertension, ante-partum haemorrhage and caesarean section) the numbers of patients in the studies included were adequate and this strengthens the validity of the findings for those parameters. Studies assessing preterm delivery, urinary tract infection, low birth weight and neonatal/infant serum iron had less than 30 patients in both the placebo and control groups, and as stated by the author, these results should be interpreted with caution.

The studies included in the review were evaluated for methodological quality and appropriateness without consideration of results. This would have prevented any selection bias with regard to these studies. Some of the studies do not describe selection of patients adequately, which would most likely not lead to significant bias as most of the studies were double blind. Studies selected for analysis of antepartum haemorrhage, preterm delivery, low birth weight, neonatal unit admission, stillbirth/neonatal death were all conducted in the United Kingdom, which may well have resulted in bias as the findings in these studies may not necessarily apply to situations in which resources may be somewhat limited as would be the situation in developing countries.

Overall, however, the results appear to have been correctly interpreted.

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