Folic acid in the prevention of birth defects.

Maternal use of folic acid prior to conception reduces the risk for neural tube defects. In addition, other birth defects may be prevented by the periconceptional use of folic acid. Homocysteine-methionine metabolism appears to be altered in women with pregnancies affected by neural tube defects; however, the specific mechanisms of causation are not yet known. Fortification of flour with folic acid has been approved by the Food and Drug Administration, although at a level that still requires folic acid supplementation as recommended by the Public Health Service for all women of childbearing age to prevent neural tube defects.