Human placental corticotropin-releasing factor (CRF) in the adaptive response to pregnancy

Several findings suggest a role of placental hormones in the regulation of maternal and fetal physiology during pregnancy. The placenta and its accessory membranes, amnion and chorion, although of fetal origin, actually undertake the role of intermediary barriers and active messengers in the maternal-fetal dialogue. They synthesize, metabolize and serve as targets for numerous hormones and cytokines which control all aspects of pregnancy and parturition. Among these, corticotropin-releasing factor (CRF) has been one of the most investigated in the last decade. The secretion of placental CRF is autonomous, but increasing evidence indicates that maternal or fetal physiological and pathological conditions may influence such secretion. In the event of acute or chronic metabolic, physical or infection stress, the placenta takes part in a stress syndrome by releasing CRF, which may contribute to restore local blood flow, and to influence the timing of delivery. Placental CRF and cytokines produced in case of intrauterine infection may activate labour, thereby helping the fetus to escape from a hostile environment.On the background of maternal and/or fetal stress elicited by a number of pathological conditions, CRF appears to play a role in coordinating adaptive changes in uterine perfusion,maternal metabolism, fluid balance and possibly uterine contractility.