Fetal-maternal distribution of ovine alpha-fetoprotein.

The concentration of ovine alpha-fetoprotein (AFP) was determined in sheep fetal, maternal, and neonatal sera and amniotic fluid by radioimmunoassay. The fetal serum AFP concentration was highest during the first third of pregnancy and continued to decline with fetal and neonatal development. Total fetal synthesis of AFP was highest during the late middle and early latter third of pregnancy. Amniotic fluid AFP concentration was highest during the early middle third of pregnancy. Maternal serum AFP was not elevated above nonpregnant control levels during the first two-thirds of pregnancy, but instead showed a tendency to be elevated only during the last third of pregnancy. The fetal physiological distributions of ovine and human AFP in fetal serum and amniotic fluid appear to be similar, whereas in maternal serum the pattern of AFP levels differs in the two species as a function of gestational age.