Phenolic Steroids in Human Subjects III. Estrogens in Plasma of Pregnant Women.

Abstract
By means of countercurrent distribution and paper chromatography, estrone, estradiol and estriol were separated from extracts of one to 2 liters of human pregnancy plasma, quantitated and identified by fluorimetric and isotopic technics. Concentration of estrone and estriol remained more nearly constant (3–9 μg/100 ml of plasma) through second and third trimesters, but the concentration of estradiol varied from 0–8 μg/100 ml.