Fetal Plasma Steroids in Relation to Parturition

Summary Total plasma corticosteroid levels were measured by a competitive protein‐binding technique in matched umbilical arterial and venous samples obtained from 234 infants immediately following vaginal delivery. Both arterial and venous levels were related to the gestational age of the infant at delivery, rising to a peak at 37 to 38 weeks gestational age and thereafter declining. Corticosteroid levels were generally less in infants delivered following oxytocin‐induced (or augmented) labour than in those delivered following spontaneous labour. The mean umbilical arterial levels (±S.E.) of plasma corticosteroids at 38 to 40 weeks were 213.2 ± 16.3 ng./ml. for the spontaneous labour group and 171.9 ± 12.3 ng./ml. for the oxytocin‐induced and augmented group. The corresponding mean venous levels were 242.9 ± 14.8 ng./ml. and 227.4 ± 13.2 ng./ml. The mean plasma corticosteroid level in four fetuses spontaneously miscarried at 17 to 20 weeks was 65.0 ± 21.6 ng./ml. The results suggest that the human fetal adrenal may have an active role in fetal maturation and the initiation of labour.