Maternal and amniotic fluid 17 alpha-hydroxyprogesterone levels during pregnancy: diagnosis of congenital adrenal hyperplasia in utero.

17 alpha-Hdroxyprogesterone levels (17 alpha-OHP) were measured in 70 samples of amniotic fluid and 30 samples of maternal serum obtained at different stages of normal pregnancy and in samples of maternal serum and amniotic fluid from a pregnancy with the fetus affected with congenital adrenal hyperplasia. The mean level of 17 alpha-hydroxyprogesterone in the amniotic fluid from control pregnancies was 133.9 +/- 7.6 ng. per 100 ml. (range, 25.1 to 266.6 ng. per 100 ml). The levels were significantly higher in midpregnancy (157.4 +/- 8.4 ng. per 100 ml.) than in late pregnancy (79.2 +/- 6.8 ng. per 100 ml.) (p less than 0.01). Amniotic fluid 17 alpha-OHP levels in the affected pregnancy were significantly higher than the control levels. Mean maternal 17 alpha-OHP level during early pregnancy and midpregnancy was 259.5 +/- 22 ng. per 100 ml. and there was a two-to three-fold increase after 37 weeks (672.2 +/- 61 ng. per 100 ml.) The maternal 17 alpha-OHP levels in the affected pregnancy were significantly higher than the control levels after 34 weeks, but before 34 weeks, the level was within the range seen in control pregnancies. Measurement of 17 alpha-OHP levels in the amniotic fluid before 24 weeks and maternal serum after 34 weeks can be utilized for the prenatal diagnosis of congenital adrenal hyperplasia.