The normal changes in mass and water content in fetal rhesus monkey and placenta throughout gestation

Abstract

Thirty-eight healthy pregnant rhesus monkeys and their fetuses were studied at different stages of gestation in order to characterize the normal changes in total weight and water content of the fetus and placenta of one of the higher primates. The per cent of total body water in the fetus decreases linearly from 93.1 per cent at 40 days gestation to 74.8 per cent at 158 days gestation (term). The percentage of the total water content in the placenta decreases through the first half of gestation and thereafter remains constant; it is greater than the percentage of total water in the fetus throughout the latter half of pregnancy. The changes in per cent of water content of several body fluids and of fetal liver are also presented. The data provide the bases for further studies of the forces that lead to the accumulation of a net quantity of water in the fetus during a normal gestation.