Hormonal measurements in maternal urine and amniotic fluid (AF) during pregnancy and/or at delivery correctly predicted the postnatal diagnosis of 11 beta-hydroxylase deficiency congenital adrenal hyperplasia (11 beta-OH deficiency CAH) in 7 fetuses at risk. In the 4 affected ones, maternal urinary tetrahydro-11-deoxycortisol (THS) excretion was high during the first trimester [0.3-2.2 mg/day (1.1-7.7 mumol/day)] and rose further during the third trimester [0.5-3.5 mg/day (1.8-12.3 mumol/day)] compared to urinary THS excretion in 20 normal pregnancies of the same gestational age (P less than 0.01). In 1 mother, dexamethasone administration (2 mg/day for 72 h) greatly reduced urinary THS excretion (and plasma steroid levels). Urinary THS excretion was low after delivery in these mothers, in normal pregnancies, and in parents of affected individuals [less than 0.05 mg/day (less than 0.08 mumol/day); P = NS]. However, 2 of the 3 heterozygous mothers who carried nonaffected fetuses excreted moderately increased amounts of THS during pregnancy, ranging from 0.15-0.26 mg/day (0.53-0.91 mumol/day), significantly higher than normal (P less than 0.01). Although urinary THS excretion in these mothers was similar to that in 2 mothers with affected fetuses early in pregnancy, urinary THS excretion was higher in mothers with affected compared to those with nonaffected fetuses after the first trimester (P less than 0.01). AF THS and 11-deoxycortisol concentrations were markedly elevated in pregnancies with affected fetuses (P less than 0.01), but normal in nonaffected ones. AF delta 4-androstenedione levels were high in 2 pregnancies and borderline elevated in a third. Although the AF tetrahydrocortisol and tetrahydrocortisone levels were always within the normal range, the AF THS to tetrahydrocortisol plus tetrahydrocortisone ratio was significantly elevated in all pregnancies with affected fetuses (2.8-5.5; P less than 0.01) and normal in nonaffected ones (0.48-1.2; P = NS) compared to that in 160 normal pregnancies [0.64 +/- 0.34 (+/- SD)]. AF 17-hydroxyprogesterone, testosterone, and 11-deoxycorticosterone levels were normal in all pregnancies. Maternal plasma 11-deoxycortisol and delta 4-androstenedione concentrations, determined sequentially throughout gestation, were variable and did not contribute to prenatal diagnosis. All affected infants were born hyperpigmented, 2 were large for gestational age, and the female was severely virilized. In the first week of life 2 males developed severe hypertension with seizures and adrenal insufficiency, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)