Changes in total and free concentrations of steroid hormones in the plasma of women throughout pregnancy: effects of medroxyprogesterone acetate in the first trimester

Abstract

The total (protein-bound plus free) and free concentrations of progesterone, oestradiol-17 beta and cortisol were measured serially throughout pregnancy in the plasma of two groups of women whose pregnancies went to term. Group A (n = 53) experienced an uneventful low-risk pregnancy with a spontaneous abortion rate of 8.6%. Women in group B (n = 22) were treated orally with medroxyprogesterone acetate (MPA; 80-120 mg daily) until 18 weeks gestation for threatened abortion within the first 6 weeks of pregnancy. In both groups of women the proportion of each hormone circulating in the free or unbound form remained constant despite the overall increases with occurred in total circulating hormone concentrations as pregnancy progressed. The steroid hormonal profiles in the first half of pregnancy were similar in both groups of women. However, from weeks 20 to 40 total and free progesterone concentrations were significantly (P less than 0.05 in each case) higher in group B compared with group A. Conversely, total and free oestradiol-17 beta concentrations were lower (P less than 0.005 and P less than 0.01 respectively) in group B. At this stage it is not known if these differences were attributable to the administration of MPA to women in group B or to altered placental steroidogenesis as a result of earlier uterine bleeding.