Neural tube defects

Neural tube defects (NTDs) are congenital structural abnormalities of the brain and vertebral column that occur either as an isolated malformation, along with other malformations, or as part of a genetic syndrome. Isolated (ie, nonsyndromic) NTDs occur in 1.4-2 per 1, 000 pregnancies and are the second most common major congenital anomaly worldwide (cardiac malformations are first) (1). In the United States, approximately 4, 000 fetuses are affected each year of which one third are either aborted or spontaneously lost (2). Anencephaly accounts for one half of all cases of NTDs and is incompatible with life; with treatment, 80-90% of infants with spina bifida survive with varying degrees of disability (2, 3). Most importantly, NTDs are among the few birth defects for which primary prevention is possible; prenatal screening and diagnosis are widely available, and prenatal therapy is being investigated.