Inhibin A and activin A in the first trimester of human pregnancy.

Recent studies show that high concentrations of inhibin A and activin A are present in the maternal serum throughout human pregnancy. The aim of this study was to determine whether the corpus luteum produces significant quantities of inhibin A and activin A during the first trimester of pregnancy. This prospective study examined two groups of women who had blood samples taken from 5-12 weeks gestation. One group consisted of 14 women with donor egg pregnancies (8 singletons and 6 multiples) who did not have corpora lutea, and the other group consisted 5 women with spontaneous pregnancies who had corpora lutea. Inhibin A and activin A were measured at weekly intervals using specific enzyme immunoassays. All pregnancies progressed to term, with healthy babies being delivered. Maternal serum concentrations of inhibin A significantly increased throughout the study period in the donor egg pregnancies (P < 0.001) and the control pregnancies (P < 0.001). Circulating concentrations of activin A also increased significantly in both the spontaneous and donor egg pregnancies (P < 0.001) during the study period. However, the concentrations of inhibin A and activin A in the first trimester of human pregnancy were not significantly different in the women with or without corpora lutea, suggesting a fetoplacental origin. Multiple donor egg pregnancies were found to have higher concentrations of inhibin A (P < 0.001) and activin A (P < 0.05) compared with singleton donor egg pregnancies, which also supports a placental source.