Diagnosis and prevention of neural tube defects.

Abstract

Neural tube defects, including anencephaly, meningomyelocele and encephalocele, are among the most common birth defects that result in severe mortality and morbidity. Neural tube defects occur with an incidence of 1-5 per 1000 births, showing marked geographic, ethnic and temporal variations. Although clear evidence exists on preventability of a large proportion of neural tube defects by periconceptional folic acid intake, only a low percentage of women are following the recommendations. In the past few decades diagnostic modalities have undergone a change from blood screening tests, such as alpha-fetoprotein, to imaging methods. Ultrasound has become the standard tool for early diagnosis, whereas fetal magnetic resonance imaging has gained importance in evaluating distinct coexisting anomalies of the central nervous system. Since the United States authorized the addition of folic acid to grain products in 1996, many other countries are considering folic acid fortification of their grain products, or have started fortification. Hitherto there is no consensus either to the duration of supplementation or to the best dose. Ultrasound and magnetic resonance imaging offer the possibility of early and accurate diagnosis of neural tube defects, and have therefore improved medical counseling and parents' decision making. Food fortification is the most practical way of ensuring sufficient folate supplementation and is warranted during the periconceptional period.