Cortisol, 11-desoxycortisol, and 21-desoxycortisol concentrations in amniotic fluid during normal pregnancy.

Concentrations of unconjugated cortisol, 11-desoxycortisol, and 21-desoxycortisol were measured by radioimmunoassay in amniotic fluid throughout gestation. Cortisol levels rose from a median of 6.5 nanograms per milliliter prior to 20 weeks to 13.9 ng/ml at 28 to 37 weeks. Median levels of 11-desoxycortisol and 21-desoxycortisol were 2.6 ng/ml and 0.21 ng/ml, respectively, and did not change with advancing gestation. These normal values provide a basis for the application of assays of 11-desoxycortisol and 21-desoxycortisol in amniotic fluid in the prenatal diagnosis of congenital adrenal hyperplasia.