A semi-automated serum alphafetoprotein radioimmunoassay for prenatal spina bifida screening.

A simple, reliable, semi-automated and inexpensive radioimmunoassay for serum alphafetoprotein (AFP) is described which fulfils the requirements for a screening test for open neural tube defects. The normal range for serum AFP throughout pregnancy has been determined in 1534 samples. In a retrospective study of 15 samples of maternal serum taken from nine pregnant women carrying a fetus affected with a neural tube defect, the serum AFP level was found to be above the 95th centile in four of the five cases of open defect sampled between 15 and 20 weeeks gestation. Preliminary results of a prospective study are reported in which two cases of nencephaly were detected among 671 unselected pregnancies sampled between 15 and 20 weeks gestation.