Results and benefits of a maternal serum alpha-fetoprotein screening program.

Maternal serum alpha-fetoprotein (MSAFP) screening was offered in a private suburban practice to 21,000 nondiabetic and 442 diabetic women with apparently normal pregnancies. Using 2.5 or greater multiples of the median as the normal upper limit, 249 (1.2%) had a raised MSAFP level. There were 25 neural tube defects (NTDs) (1.2/1,000 births); 18 were detected by screening and two by ultrasound scanning. Three had closed spina bifida lesions. Two had anencephaly with normal MSAFP levels, but were studied at more than 24 weeks' gestation. An additional 13 with raised MSAFP levels had other congenital defects. One in 400 women screened had a recommended amniocentesis; 26.4% of them had a fetus with an NTD or major malformation. Our detection efficiency before 24 weeks' gestation for anencephaly was 85.7% (12/14), 62.5% (5/8) for open and closed spina bifida, and 1/1 for encephalocele. A raised MSAFP level occurred in ten (2.3%) of the 442 diabetic women, four (0.9%) of whom had a fetus with an open NTS. A screening program should be established only where there is linked excellent interdisciplinary support among obstetrician, laboratory, clinical geneticist, ultrasonographer, and an identified program coordinator.