Prenatal diagnosis of fetal sex by amniotic fluid testosterone and FSH, and their potential use in detecting sex linked disorders.

Amniotic fluid testosterone was assayed by radioimmunoassay in 971 samples at 16-18 weeks gestation. FSH assay was performed in 353 of these samples. Correct prediction of fetal sex (46%) was made in all samples with a testosterone level above 338 ng/L for all males, and below 162 ng/L for females. For 45% of samples with FSH levels below 7.6 IU/L for males and 10.9 IU/L for females the fetal sex was predicted correctly. By using a testosterone/FSH ratio, the diagnostic accuracy was 80%. The anmiotic fluid of ten Duchenne Muscular Dystrophy carrier mothers were studied and only the sex of one case could not be predicted. The amniotic fluid testosterone and FSH assays could be used as a rapid biochemical screening method for predicting fetal sex in X-linked disorders before birth.