Prenatal diagnosis of neural tube defects.

Neural tube defects are relatively common congenital malformations. An assay is available which permits prenatal screening of maternal serum for alpha-fetoprotein (AFP). Elevated AFP levels are associated with neural tube defects and other developmental abnormalities. Two positive blood tests indicate the need for ultrasonography. Further diagnostic testing of amniotic fluid for AFP and acetylcholinesterase levels may be necessary to confirm a neural tube defect.