Adrenal cortical function in the postmature fetus and newborn infant.

The umbilical venous blood concentrations of cortisol, dehydroepiandrosterone sulfate (DHAS), and unconjugated estriol were compared in 54 normal, 37 postterm, and 22 postmature newborns. Pre- and postadrenocorticotropic hormone (ACTH) stimulation levels of serum cortisol and DHAS were compared in the first 2 to 4 days of life in 19 postterm and 15 postmature infants. Comparison was also made between vaginally an cesarean section delivered postterm and postmature newborns. There were significantly greater cord blood cortisol levels in th postmature [260 +/- 22 ng/ml (+/- S.E.)], than in the normal (193 +/- 11 ng/ml) (P less than 0.01) or postterm (193 +/- 18 ng/ml) (0.01 less than P less than 0.05) vaginally delivered infants. There were no significant differences in the mean cord blood DHAS levels in the three groups (normal, 2645 +/- 130 ng/ml; postterm 2323 +/- 188 ng/ml; postmature, 2310 +/- 224 ng/ml). Cortisol and DHAS responses to ACTH stimulation were the same in the postterm and postmature groups. There was a significantly lower mean umbilical venous unconjugated estriol level in the vaginally delivered postmature group (75 +/- 11 ng/ml) as compared to values in vaginally delivered postterm [120 +/- 14 ng/ml (P = 0.01)] and normal [144 +/- 10 ng/ml (P less than 0.002)] newborns. Stressed postmature infants delivered by cesarean section had higher unconjugated estriol levels (83 +/- 12 ng/ml) than their unstressed, postterm cesarean section controls [40 +/- 9 ng/ml (P less than 0.01)], but levels were still below those from vaginally delivered postterm infants. These findings substantiate normal adrenal function in the postmature fetus and newborn. Lowered umbilical venous unconjugated estriol levels in the postmature infants at birth appear to be a function of limited aromatizing activity of the placenta rather than due to the low levels of fetal adrenal-derived neutral steroid substrate.