In situ perfusion of human midtrimester placentas with labled pregnenolone and 17α-hydroxypregnenolone was carried out. Following perfusion with pregnenolone, the bulk of the radioactive material recovered from the placenta, and approximately one-fourth of that recovered from the venous effluent, was progesterone. Perfusion with 17α-hydroxypregnenolone resulted in a similar conversion to 17α-hydroxyprogesterone. It is suggested in conversion of circulating 3β-hydroxy-∆5 precursors into α, β unsaturated 3-ketones may be a major pathway in the placental synthesis of progesterone and 17α-hydroxyprogesterone. In addition, using a variety of experimental techniques, including perfusion of placentas in situ, injection into the intact feto-placental unit via the umbilical vein, as well as long-term administration into the amniotic sac and antecubital vein of the mother, very little, if any, estrone-, 17β-estradiol-, or estriol-like radioactive material could be detected in the placenta, fetal tissues and urine of the mother following the administration of labeled progesterone. These results are interrupted as supporting the concept that progesterone is not a significant precursor of placental estrogens.
Jaffe, Robert Benton, "Aspects of C-21 Steroid Biogenesis and Metabolism in the Human Fetus and Placenta in the Second Trimester of Pregnancy" (1966). University Libraries Digitized Theses 189x-20xx. 55.