Conjugated and Unconjugated Estrogens in Fetal and Maternal Fluids of the Pregnant Ewe: A Possible Role for Estrone Sulfate during Early Pregnancy1

Abstract

The concentration of the unconjugated and sulfoconjugated estrogens have been measured in the fetal and maternal fluids of the ewe throughout pregnancy. Estrone sulfate was the major estrogen in all the fluids examined. In the fetal fluids, it was first detectable in allantoic fluid on Day 31, peaked at a high level (14.2 ng/ml) on Day 46 and declined rapidly to 850 pg/ml at Day 55 before gradually rising to a second high level. The concentration in amniotic fluid followed that in allantoic fluid, but no second peak was evident. The pattern for the concentration of unconjugated estrone was similar to that of the sulfoconjugate, but at a very much lower level. The change in the concentration of the estradiol sulfates was similar to that for estrone sulfate. An estimate was obtained for the radio of the amounts of estradiol-17α to estradiol-17β which were present. In the maternal fluids, estrone sulfate was again the major estrogen present, but it was not readily detectable in the jugular venous plasma until approximately Day 50. The possible roles of estrogen during early pregnancy are discussed.