Studies on human sexual development. V. Concentrations of testosterone, 17-hydroxyprogesterone and progesterone in...

Concentrations of unconjugated testosterone, 17-hydroxyprogesterone (170HP) and progesterone were measured by radioimmunoassay in amniotic fluid (AF) specimens from normal pregnancies of 9-40 weeks gestation. In two-thirds of samples from pregnancies with male fetuses. AF testosterone exceeded the upper limit found in female samples, with minimal overlap in the 12-18 week period of gestation. Although AF testosterone levels associated with male and female fetuses were both significantly lower toward term, the sex-difference persisted. Between 9-19 weeks gestation, fetal sex was also found to influence AF 170HP, a steroid thought to be predominantly of placental and fetal adrenal origin; in this case, female levels exceeded male. Awareness of the influence of sex and gestation upon AF concentrations of these steroids is an important prerequisite for their application to the prenatal diagnosis of endocrine disease (e.g., congenital adrenal hyperplasia). There was no sex difference in AF progesterone concentrations at 12-18 weeks gestation. The median progesterone concentration at 34-40 weeks was higher with female fetuses, but this difference may be related to a difference in gestational age between AF samples obtained from male and female fetuses.