Amniotic fluid testosterone in prenatal sex determination.

Nonconjugated testosterone levels were measured by radioimmunoassay in samples of amniotic fluid from 60 normal pregnant women between 15 and 32 weeks of gestation. In the male fetuses, the mean +/- SEM amniotic fluid testosterone levels(328 +/- 25 pg/ml) were significantly higher (p less than 0,001) than the concentrations found in the female fetuses (121 +/- 9 pg/ml). The ranges were from 155 to 730 and from 46 to 240 pg/ml respectively, which shows an overlap area of the values between the sexes from 155 to 240 pg/ml. The results emphasize the potential interest of amniotic testosterone in the determination of fetal sex.