Amniotic fluid follicle-stimulating hormone and fetal sex determination in the second trimester of pregnancy

Summary

The concentration of follicle-stimulating hormone (FSH) in amniotic fluid was measured in 101 patients whose gestational age ranged from 11 to 22 weeks; 48 of the fetuses were male and 53 were female. Both sexes had low amniotic fluid FSH levels between 11 and 13 weeks. After 13 weeks, amniotic fluid FSH values remained low with a male fetus, but there was a significant rise with a female fetus. The mean amniotic fluid FSH concentration in patients with a female fetus was five times higher than in patients with a male fetus. In this age group, none of the 35 patients with a male fetus had amniotic fluid FSH values which were higher than 23 μg/1, whereas 22 of the 41 patients with a female fetus had values above 23 μg/1 (56 per cent). With amniotic fluid FSH concentrations higher than 23 pg/1, the presence of a female fetus could thus be predicted.