Prenatal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency by amniotic fluid steroid analysis.

The concentration of 17OH-progesterone was measured in second trimester amniotic fluid samples from 12 mothers who previously had had an infant with congenital adrenal hyperplasia due to 21-hydroxylase deficiency. In 4 affected pregnancies, the concentrations were more than 2 S.D. higher than those determined in 44 samples from normal pregnancies (mean +/- S.D., 8.1 +/- 2.4 nmol/l). The remaining 8 pregnancies were predicted to be unaffected based on the results of amniotic fluid concentrations within the normal range. In each instance, the infant was normal. The results indicate that measurement of amniotic fluid 17OH-progesterone concentrations during the second trimester is an accurate prenatal test for 21-hydroxylase deficiency. The results should be supplemented with determination of fetal sex by karyotype analysis on the amniotic fluid cells.