Background: Neural tube defects arise during the development of the brain and spinal cord.
Objectives: The objective of this review was to assess the effects of increased consumption of multivitamins or folate on the prevalence of neural tube defects before pregnancy and in the first two months of pregnancy (periconceptionally).
Search strategy: We searched the Cochrane Pregnancy and Childbirth Group trials register.
Selection criteria: Randomised and quasi-randomised trials comparing periconceptional supplementation by multivitamins with placebo, folate with placebo, or multivitamins with folate; different dosages of multivitamins or folate; prepregnancy dietary advice and counselling in primary care settings to increase the consumption of folate-rich foods, or folate-fortified foods, with standard care; increased intensity of information provision with standard public health dissemination.
Data collection and analysis: Two reviewers assessed trial quality and extracted data.
Main results: Four trials involving 6425 women were included. The trials all addressed the question of supplementation and they were of variable quality. No dissemination trials were identified. Periconceptional folate supplementation reduced the incidence of neural tube defects (odds ratio 0.28, 95% confidence interval 0.15 to 0.53). Folate supplementation did not significantly increase spontaneous abortion, ectopic pregnancy or stillbirth, although there was a possible increase in multiple gestation. Multivitamins alone were not associated with prevention of neural tube defects and did not produce preventive effects when given with folate.
Reviewer's conclusions: Periconceptional folate supplementation has a strong protective effect against neural tube defects. Information about folate should be made more widely available throughout the health and education systems. Women whose fetuses or babies have neural tube defects should be offered continuing folate supplementation. The benefits and risks of fortifying basic food stuffs, such as flour, with added folate remain unresolved.