Adrenal cortical function in the postmature fetus and newborn infant

Abstract

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 IS postmature infants. Comparison was also made between vaginally and cesarean section delivered postterm and postmature newborns. There were significantly greater cord blood cortisol levels in the post- mature 1260 ± 22 ng/ml (±S.E.), than in the normal (193 ±11 ng/ml) (P < 0.01) or postterm (193 ± 18 ng/ml) (0.01 < P < 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)1 and normal [144 ± 10 ng/ml (P < 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 < 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 low levels of fetal adrenal-derived neutral steroid substrate. Speculation: Early in the development of placental insufficiency, placental conversion of fetal-derived neutral steroid estrogen precursors is the limiting factor in estrogen production in the feto-placental unit. Whether estrogen precursor production by the fetus also becomes an important factor in decreased feto-placental estrogen production as placental insufficiency progresses has not been determined. © 1980 International Pediatric Research Foundation, Inc.