Hormonal changes during the perinatal period: FSH, prolactin and some steroid hormones in the cord blood and peripheral serum of preterm and fullterm female infants.

Fetoplacental endocrine function during the last third of gestation, and first 5 days post partum, was studied by hormone measurements of umbilical cord arterial and venous serum in preterm (31-37 weeks gestation) and fullterm (39-42 weeks gestation) female newborn. Furthermore, hormones were measured in peripheral serum of fullterm female infants of 1, 3 and 5 days of age. The data were compared with those obtained previously in corresponding age groups of males. FSH was significantly (P less than 0.05) higher in the cord serum of preterm females (5.4 +/- 1.8 IU/I, SE, n = 30) than in males (1.5 +/- 0.08 IU/l, n = 27), and decreased significantly (P less than 0.05) in preterm females towards fullterm. PRL levels increased in both sexes towards the end of gestation (P less than 0.01), and decreased post partum, but no sex differences could be detected. Testosterone was significantly higher in the male serum samples (P less than 0.01-0.05), but only minor sex differences were seen in cord serum, or post partum, concentrations of the other steroids measured, pregnenolone, progesterone, 17-hydroxyprogesterone and androstenedione. Significant arterio-venous difference (higher in the vein) were seen at term in progesterone and 17-hydroxyprogesterone. The levels of these two steroids also decreased most clearly after birth. Female serum testosterone peaked at d 1 post partum (0.084 +/- 0.014 microgram/l, SE, n = 11), decreased thereafter, but remained at the intrauterine level, suggesting that the low female levels of this steroid are of fetal, rather than placental/maternal origin. The same seems to be true for androstenedione. Our data suggest that the fetal ovary is quiescent during the last weeks of gestation.