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.