Levels of alpha-fetoprotein in maternal blood as a screening test for fetal neural-tube defect.

A range has been established for maternal plasma-alpha-fetoprotein (A.F.P.) levels in normal pregnancies (930 women). A.F.P. levels between 10 and 40 weeks gestation were examined in 51 pregnancies associated with fetal neural-tube defect. In 96% of cases (20 anencephalus, 6 spina bifida) examined between 16 and 26 weeks of gestation A.F.P. levels were above the 95th centile of the normal range. It is suggested that measurement of A.F.P. in maternal blood should become a screening test in all pregnancies, and a scheme for the futher investigation of patients with abnormal results is described.