Maternal serum alpha-fetoprotein and fetal autosomal trisomies.

Maternal serum alpha-fetoprotein values in 61 patients with fetal autosomal trisomies diagnosed at 6581 genetic amniocenteses were significantly lower than those in an equal number of matched control subjects. The genetic risk of fetal autosomal trisomies for women less than age 35 offered amniocentesis with maternal serum alpha-fetoprotein values less than 0.5 multiples of the median is in the same range as that currently accepted for advanced maternal age. Maternal serum alpha-fetoprotein screening for autosomal trisomies (mainly Down syndrome) is feasible.