Corticotropin-releasing hormone (CRH), the principal regulator of the hypothalamic-pituitary-adrenal axis, as well as its receptors, have been identified in most female reproductive tissues, including the uterus, placenta, and ovary. Endometrial CRH may participate in decidualization, implantation, and early maternal tolerance; placental CRH may participate in the physiology of pregnancy and the onset of parturition, and ovarian CRH may participate in follicular maturation, ovulation, and luteolysis. The hypercortisolism of the latter half of pregnancy can be explained by increased levels of placental CRH in plasma. This hypercortisolism is followed by a transient suppression of hypothalamic CRH secretion in the postpartum period, which may explain the blues or depression and autoimmune phenomena frequently observed during this period.