Maternal and fetal plasma levels of free corticosteroids in pathological deliveries.

Does intrauterine acidosis induce increased steroid secretion? The concentration of free steroids (CS) increases in both fetal and maternal plasma during labor and delivery. Fetal levels are higher after vaginal than after cesarean section. These differences may indicate an important role of the fetal adrenal gland in the induction of labor or they may reflect merely the fetal response to the stress of delivery. During incrased intrauterine stress steroid secretion is increased as shown here. We examined 41 mothers and their infants during pathological labor. Pathology was assessed from fetal acidosis and/or a clinically obstetric disease of the mother or fetus. The 41 cases included 9 cesarean sections, 8 forceps deliveries; 24 spontaneous deliveries of which 7 were premature. At the time of delivery the pH and CS level were determined in maternal and umbilical vessels in all cases. During spontaneous labor blood samples were also taken during the different stages of labour. A competetive protein binding assay with transcortin without fractionation of the steroids was used. Progesteron was determined by the same assay. The level of this hormone, however, remains unchanged and hence any changes reflect changes in CS. The levels of CS were correlated with the pH values and compared to previously obtained normal values. During pathological deliveries CS levels in both mother and fetus are normal as long as there is no acidosis (Fig. 1). If acidosis is present the CS level in the umbilical artery is usually higher than normal. In 13 out of 18 vaginal deliveries the CS level was above normal, in the other 5 at the upper limit of normal (Fig. 1 and 2). At the same time the a--v difference becomes smaller and sometimes even negative. No changes were noted in maternal and umbilical venous blood (Tab. I and II). Similar dependence on the pH was found for cesarean sections (Tab. III). In premature deliveries without acidosis in the umbilical artery the CS levels were lower in both mother and fetus (Tab. I). These results indicate that the fetal adrenal gland reacts to acidosis, i.e., intrauterine stress, with increased corticosteroid secretion. This rise depends on the pH of fetal blood and not on the type of delivery (Fig. 3).