Maternal testosterone and fetal sex.

To investigate the influence of fetal sex on maternal testosterone levels throughout pregnancy, blood was sampled from 37 healthy pregnant women from week 14 until term and at 6 weeks postpartum. Testosterone concentrations were measured with a highly specific RIA after chromatographic purification. Mean (+/- SD) testosterone at the end of gestation was significantly higher compared to non-pregnant values (3.10 +/- 2.38 mM/l, n = 32 vs 1.14 +/- 1.06 nM/l, n = 35). It appeared that in women carrying a male fetus testosterone levels gradually increased during pregnancy up to 3.99 +/- 2.72 nM/l. In women carrying a female fetus the levels decreased after the first trimester from 2.44 nM/l to 1.80 nM/l. A statistically significant difference (P less than 0.01) existed in maternal testosterone concentrations between both groups during the second half of pregnancy.