MATERNAL PLASMA ALPHAFETOPROTEIN LEVELS IN THE SECOND HALF OF NORMAL PREGNANCY: RELATIONSHIP TO FETAL WEIGHT, AND MATERNAL AGE AND PARITY

Abstract
A semi-automated radioimmunoassay for plasma alphafetoprotein has been developed, suitable for routine clinical use. Several hundred samples can be assayed in a working week, with results available within 24 hours. The use of extensive quality controls ensures that good precision is maintained both within and between assays. The range of plasma concentrations of alphafetoprotein in the second half of pregnancy has been established in 100 normal subjects. The levels rise progressively to reach a peak at 32 weeks, and thereafter fall until term. No relationship between circulating alphafetoprotein levels and birth weight was observed.