Interrelationship of Estrogen Concentrations in the Maternal Circulation, Fetal Circulation and Maternal Urine in Late Pregnancy

Abstract

The levels of estrone, estradiol-17β and estriol in plasma obtained from umbilical artery, umbilical vein, maternal brachial artery (or peripheral vein) and uterine vein have been estimated in a series of subjects at cesarean section and at normal delivery. Levels of estrone and estradiol-17β were higher in the umbilical vein than in the umbilical artery, presumably reflecting secretion of these hormones by the placenta and subsequent metabolism by the fetus. Comparison of estrogen concentrations in maternal and fetal circulations showed that concentrations of estrone and estradiol-17β were 2–4 times higher in the maternal than in the fetal vessels, whereas the concentration of estriol in the fetal vessels was 9–12 times higher than in the maternal. These concentration differences were shown to exist generally across the placenta. They do not necessarily reflect concentration gradients. Concentrations of estradiol-17β and estriol are significantly higher in the uterine vein than in maternal brachial arter...