Placental secretion of oestrogens and protein hormones.

In order to trace the passage of steroids and proteins from the placenta to the maternal peripheral blood, samples of retroplacental blood, uterine vein blood and peripheral blood were taken from women undergoing Caesarean section at term. The concentration of unconjugated oestriol, total oestriol, human placental lactogen and pregnancy specific beta1 glycoprotein was measured. The oestrogen concentration in the uterine vein was higher than the peripheral blood, the placental lactogen was slightly higher and the pregnancy specific beta1 glycoprotein was the same in the uterine vein and the peripheral veins. In keeping with this, the retroplacental blood had a high concentration of oestrogen, moderately raised placental lactogen and a low pregnancy specific glycoprotein concentration. It is concluded that there is a rapid secretion of oestriol from placenta to the mother; a slower secretion of placental lactogen and no clear evidence of a flow of pregnancy specific glycoprotein from the placenta.