Folic acid supplements in pregnancy and birth outcome: re-analysis of a large randomised controlled trial and update of Cochrane review

Periconceptual folic acid prevents neural tube defects. The effect of folic acid taken throughout pregnancy is unclear, however. We re-analysed data from a large randomised controlled trial performed between 1966 and 1967 and combined the results with those from trials included in a Cochrane review. A total of 2928 women were randomised: 1977 were allocated to placebo, 466 to folic acid 200 mu g/day and 485 to folic acid 5 mg/day. Folic acid supplementation was not associated with any difference in mean birth-weight, placental weight or gestational age. When combined with trials in the Cochrane. review folic acid at high doses was associated with reduced risk of low birthweight (pooled relative risk 0.73 [95% Cl 0.53, 0.99]). We found no conclusive evidence of benefit for folic acid supplementation in pregnant women given from time of booking onwards.