Neural tube defects (NTDs) are among the most common birth defects that result in infant mortality and serious disability. NTDs, which include anencephaly, spina bifida, and encephalocele, occur in approximately 1 of 1000 births in the United States.1,2 Before the recent data showing that a large proportion of spina bifida with other NTDs can be prevented by folic acid, a specific cause (eg, chromosomal or Mendelian disorder) could be identified in only a small fraction of cases, and the causes of most NTDs were unknown.3 Most NTDs occur as isolated defects, rather than in association with multiple malformations. Among US couples who have had a previous child with an NTD, the recurrence rate is 2% to 3% in subsequent pregnancies. Ninety-five percent of children with an NTD are born to couples with no family history of any of these defects.
Several earlier studies have suggested that folic acid supplementation may prevent the recurrence of NTDs.4-8 The findings were controversial because of the lack of large, well-designed, prospective, randomized studies. In 1991, the Medical Research Council (MRC) Vitamin Study Group reported the results of a well-designed, prospective, randomized study of folic acid supplementation for the prevention of NTDs in pregnancies of high-risk patients (ie, those who had a previous child with an NTD) who were predominantly from the United Kingdom (UK) and Hungary, but also from five other countries.9 The data conclusively demonstrated that daily 4-mg doses of folic acid before and during early pregnancy resulted in a 71 % reduction of recurrence of NTDs in this group of high-risk pregnancies.
- Copyright © 1993 by the American Academy of Pediatrics