Changes in maternal plasma levels of C21 and C19 steroid hormones during pregnancy

: To study the changes in circulating steroid levels during pregnancy, ten steroids which included Progesterone (P4), 16 alpha OH-Progesterone (16P4), free and conjugated Pregnenolone (P5), 16 alpha OH-Pregnenolone (16P5), Dehydroepiandrosterone (DHA) and 16 alpha OH-Dehydroepiandrosterone (16DHA) were measured simultaneously by RIA in 84 normal pregnant women from the 5th to 41st week of gestation. Ratios steroid levels were also calculated. The results were as follows; 1. P4 increased as gestation advanced and reached the maximum (126 +/- 18.24 ng/ml) in the 28th week. The concentration 16P4 increased sharply after the 32nd week and reached the maximum (16.3 +/- 1.67 ng/ml) in the 39th week. 2. Both free and conjugated P5 levels did not show an increasing trend as pregnancy progresses. 3. The concentration of free and conjugated 16P5 increased rapidly after the 30th week and reached the maximum at 39th week (free 2.5 +/- 0.3 ng/ml conjugated 42.4 +/- 5.1 ng/ml). 4. Both free and conjugated DHA decreased as pregnancy progressed. On the other hand, the concentration of free and conjugated 16DHA increased as pregnancy progressed. 5. The ratio of 16P4 to P4, 16P5 to P5 and 16DHA to DHA significantly increased after 30 weeks of gestation.