Raised maternal serum alpha-fetoprotein in the absence of fetal abnormality--placental findings. A quantitative morphometric study.

Ten placentae from pregnancies proceeding to term from mothers who on routine screening at 16-18 weeks gestation were found to have raised serum AFP but no increase in amniotic fluid AFP and no fetal abnormality, were studied using morphometric techniques. The results were compared with 20 placentae from normal term pregnancies where the maternal serum AFP level was not elevated. The mean total placental volume, volume of parenchyma and villous surface area were increased in the placentae associated with a raised maternal serum AFP. More of these placentae were infarcted and the fetal-placental weight ratio was significantly lower. The hypothesis that elevation of maternal serum AFP level is related to the increase in placental size is addressed.