Data from an alpha-fetoprotein pilot screening program in Maine.

In Maine, maternal serum alpha-fetoprotein (AFP) values equaled 2 or more multiples of the median in 4.8% of screened women. Between 2.0 and 2.9 multiples of the median repeat maternal serum AFP testing and sonography were comparable as the next diagnostic step; at 3 multiples of the median or higher sonography was superior. Sonography moved dates back in only ten singleton viable pregnancies with maternal serum AFP elevations; three of these had open fetal defects. Among singletons, all five anencephaly cases, one of two open spina bifida lesions, and all three open ventral wall defects were identified. Three closed singleton neural tube defects and two open spina bifida defects in twins were not detected. Nineteen of 36 multiple gestations had maternal serum AFP 2 or higher multiples of the median. In singletons, maternal serum AFP of 3 or higher multiples of the median indicated a thirtyfold increased risk for fetal death and a sevenfold increased risk for birth weight under 2500 g.