Potential roles of decidual prolactin in early pregnancy

Successful establishment of pregnancy is dependent on uterine receptivity a t the time of trophoblast invasion and implantation. The endometrium underg oes morphological and Functional differentiation during the mid- to late se cretory phase of the menstrual cycle in preparation for such an event. Thes e changes are orchestrated by ovarian steroid hormones. However, local auto crine-paracrine signalling at the deciduo-placental interface is crucial fo r successful establishment of pregnancy. One key cytokine that may regulate many functions in implantation is prolactin. Prolactin is secreted by the decidualized endometrium at the time of predicted conception and, in the ev ent of pregnancy, local expression and secretion of prolactin persists unti l term. Prolactin mediates its effect on target cells through interaction w ith single-pass transmembrane receptors. Localization of the sites of expre ssion of the prolactin receptor indicates that the cytokine may regulate an array of functions in the pregnant uterus that are crucial in implantation and early pregnancy.