Inhibin-related proteins are involved in the control of the feto-maternal communication required to maintain pregnancy. Human placenta, decidua, and fetal membranes are the major sites of production and secretion of activin A, inhibin A and inhibin B in maternal serum, amniotic fluid, and cord blood. The availability of suitable assays developed in the last years has enabled the measurement of inhibins and activin A in their dimeric forms, in order to investigate their role in physiological conditions of pregnancy. The studies conducted on inhibin-related proteins and human pregnancy suggested the possibility of an involvement of inhibin A and activin A in the pathogenesis of gestational diseases. In fact, several lines of evidence underline the potential role and the clinical usefulness of inhibin-related proteins measurement in the diagnosis, prevention, prognosis and follow-up of different gestational pathologies such as early pregnancy viability, Down's syndrome, fetal demise, pre-eclampsia, pregnancy-induced hypertension, preterm delivery and intrauterine growth restriction. The measurement of inhibin A and activin A into the biological fluids of pregnancy will offer in the future, further possibilities in the early diagnosis, prediction, and monitoring diseases of pregnancy.