Effects of parturition on corticotropin releasing hormone and products of the pituitary and adrenal in term fetuses at delivery.

Corticotropin releasing hormone (CRH), a hypothalamic hormone which regulates pituitary-adrenal function, is also produced by the human placenta. We studied umbilical cord concentrations of CRH to determine whether placental secretion of this hormone into the fetal compartment is altered during parturition. We also measured adrenocorticotropic hormone (ACTH), cortisol and dehydroepiandro-sterone sulfate (DHEAS) to determine whether levels of these pituitary and adrenal hormones were correlated to CRH in the fetal plasma. Blood was obtained from umbilical cords of 111 healthy term fetuses at delivery. Concentrations of CRH, ACTH, cortisol and DHEAS were measured by radio-immunoassay. Hormone levels were analyzed according to the presence of labor and delivery mode. In addition correlations between different hormones were determined. Fetal plasma CRH levels were similar for all conditions of labor and delivery as were levels of DHEAS. Fetal plasma ACTH and cortisol were increased after vaginal delivery. There were no significant correlations between placental CRH, ACTH and cortisol levels. However, an inverse correlation between fetal plasma CRH and DHEAS levels was found (r = -0.41, p < 0.001). Increases in ACTH during parturition are likely due to stimulated release by the fetal pituitary. Our data suggest that placental CRH does not mediate this acute response to the stress of parturition. We hypothesize that continuous stimulation of the pituitary and adrenal by circulating CRH during development may occur and the inverse correlation between fetal plasma CRH and DHEAS may be due to this chronic regulatory effect.