Screening for chromosomal anomalies with maternal serum alpha-fetoprotein

Between July 1, 1986 and January 31, 1988, genetic amniocentesis was performed on 205 patients. The maternal serum alpha-fetoprotein (AFP) and amniotic fluid AFP levels were measured by enzyme immunoassay. Gestational dates were confirmed by sonography, and AFP results were expressed as multiples of the median (MOM). The median of maternal serum AFP from 15 to 17 weeks of gestation was 43.4, 62.6 and 72.5 ng/ml. Three fetuses with chromosomal anomalies were diagnosed; trisomy 21, 4p trisomy, and trisomy 18 (trisomy 18 was in one fetus of a twin pregnancy; the other fetus was normal). Maternal serum AFP levels were, 0.41, 0.49 and 1.30 MOM. Maternal serum AFP less than 0.5 MOM in normal pregnancies was 1/205 (0.5%) and less than 0.6 MOM was 9/205 (4.4%). There was no relationship between maternal serum AFP and amniotic fluid AFP levels. Our results are in agreement with the majority of the results in the literature, showing that maternal serum AFP levels are lower in association with autosomal trisomy fetuses.