EFFICACY OF FOLIC-ACID PROPHYLAXIS FOR THE PREVENTION OF NEURAL-TUBE DEFECTS

Thirty years ago, researchers suggested that maternal intake of certai n vitamins during pregnancy affected the incidence of serious birth de fects. Since then, two randomized controlled trials and several observ ational studies have proven that if women take folic acid during the p ericonceptional period, they can lower their risk of having children w ith neural tube defects (NTDs), serious birth defects of the spine and brain. In 1992, the U.S. Public Health Service recommended that all w omen capable of becoming pregnant take 0.4 mg of folic acid daily. Tra nslating this recommendation into practice, however, presents a major public health challenge. In 1996, the U.S. Food and Drug Administratio n ruled that ''enriched'' cereal grain products must be fortified with folic acid, the first time food has been fortified for the prevention of birth defects. However, because the level chosen for folic acid fo rtification will not provide all women the optimal protection against the occurrence of NTDs, efforts to increase reproductive-age women's c onsumption of folic acid-containing vitamins and folate-rich foods are underway The mechanism underlying folic acid's efficacy in preventing NTDs is unknown. It may work by correcting a deficiency or by overcom ing an inherited disorder of folate metabolism. The role of genetics a nd agents such as vitamin B-12, methionine, and homocysteine in NTD pr evention, and the relationship of these factors with folic acid, are u nder investigation. Although the mechanism for folic acid's protective effect is unknown, it is clear that a significant proportion of NTDs can be prevented and that prevention efforts should not await the eluc idation of specific mechanisms, (C) 1998 Wiley-Liss. Inc.