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 re gulates pituitary-adrenal function, is also produced by the human plac enta. We studied umbilical cord concentrations of CRH to determine whe ther placental secretion of this hormone into the fetal compartment is altered during parturition. We also measured adrenocorticotropic horm one (ACTH), cortisol and dehydroepiandro-sterone sulfate (DHEAS) to de termine whether levels of these pituitary and adrenal hormones were co rrelated 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 radioimmunoassay. Hormone l evels were analyzed according to the presence of labor and delivery mo de. In addition correlations between different hormones were determine d. Fetal plasma CRH levels were similar for all conditions of labor an d delivery as were levels of DHEAS. Fetal plasma ACTH and cortisol wer e increased after vaginal delivery. There were no significant correlat ions between placental CRH, ACTH and cortisol levels. However, an inve rse 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 tha t placental CRH does not mediate this acute response to the stress of parturition. We hypothesize that continuous stimulation of the pituita ry 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.