The role of periconceptional vitamin supplementation in the prevention of neural tube defects.

The British Isles multicentre study of periconceptional vitamin supplementation in women with a previous infant with an NTD has demonstrated an apparent beneficial effect in reducing risk of recurrence of an NTD. In Northern Ireland, a similar significant effect has been observed with a reduction of the recurrence risk from 5.2% in unsupplemented to 0.7% in fully supplemented women. The problems and implications of periconceptional vitamin supplementation in the prevention of NTDs are discussed.