The Lack of Influence of Labor on Human Placental lljS-Hydroxysteroid Dehydrogenase Activity

llβ-Hydroxysteroid dehydrogenase (E.C. 1.1.1.146) activity and endogenous cortisol and cortisone concentrations were measured in samples of human placenta obtained at term: at elective cesarean section, after labor of spontaneous onset, and after labor of induced onset. Both llβ-hydroxysteroid dehydrogenase activity and the cortisol to cortisone ratios were similar in the three groups of tissues, suggesting that there are no changes in placental corticosteroid metabolism in relation to parturition. (J Clin Endocrinol Metab 54: 1251, 1982)