The steroid hormonal milieu of the undisturbed human fetus and mother at 16-20 weeks gestation.

The interrelations of steroid hormone levels in plasma and amniotic fluid from mothers and their undisturbed fetuses at early midgestation of human pregnancy have not been defined previously. We, therefore, studied 12 healthy mothers and their fetuses undergoing termination of pregnancy for social reasons at 16-20 weeks gestation. Fetal arterial and venous blood was obtained by direct vessel puncture through a fetoscope in the conscious sedated mothers immediately before termination of pregnancy. Simultaneously, maternal peripheral venous blood and amniotic fluid were collected. Aldosterone (Aldo), corticosterone (B), 11-deoxycorticosterone, progesterone (P), 17-hydroxyprogesterone (17OHP), 11-deoxycortisol, cortisol (F), and cortisone were simultaneously determined by specific RIA after extraction and chromatography. Positive fetal arterio-venous differences were found for F, B, and Aldo, whereas arteriovenous differences were negative for P and 17OHP. In amniotic fluid, six of the eight corticosteroids showed significantly lower levels during fetoscopy than during routine amniocentesis, as reported previously using the same analytical methods. The present study demonstrates that the undisturbed human fetus at 16-20 weeks gestation actively secretes the most important gluco- and mineralocorticoids, F, B, and Aldo, independent of the mother. P and 17OHP were shown to be primarily derived from placental production and supplied to the fetus as a source of F and Aldo biosynthesis. The fetoscopy procedure with premedication seemed to give rise to less stress to the fetus than routine amniocentesis without sedation. Fetoscopy is, therefore, an ideal method to study feto-maternal steroid interrelations in human pregnancy.