A study of the value of measuring maternal serum alpha-fetoprotein for the antenatal diagnosis of neural tube defects.

Two neighbouring centres, both located in an area where the prevalence of neural tube defects (NTDs) is low, were compared to determine if there was any advantage in their differing policies as regards the antenatal detection of NTDs. At both centres routine ultrasound examinations were performed at 16-18 weeks gestation but at Hospital A serum alpha-fetoprotein (AFP) was measured at 16 weeks gestation. The prevalence of NTDs was 1.3 per 1,000 births at Hospital A and 1.7 per 1,000 births at Hospital B. The detection of anencephaly at both hospitals was 100%, however, only 43% of spina bifidas were detected at Hospital A compared with 60% at Hospital B. These results, the loss of two fetuses following amniocentesis at Hospital A and the lower detection rate for NTDs at the hospital employing AFP measurement are discussed.