Maternal and fetal hypothalamo-pituitary-adrenal axis: different response depends upon the mode of parturition.

OBJECTIVES The changes in corticotropin releasing hormone (CRH), adrenocorticotropin hormone (ACTH), cortisol and dehydroepiandrosterone (DHEA) in maternal and fetal plasma were estimated in two group of women undergoing labour after oxytocin induction, or elective cesarean section to correlate changes in maternal and fetal HPA axis to the different stressor conditions. MATERIALS AND METHODS Blood was sampled from a maternal peripheral vein two days before labour, during the second stage of labour and on the second postnatal day, and also from umbilical vessels just after delivery. Hormone concentrations were measured by RIA and ELSA methods. The maternal plasma CRH concentration before and after labour was similar in both studied groups. RESULTS Plasma CRH levels measured before labour in both groups were similar, but during labour after oxytocin infusion declined, and was in group of women with elective cesarean section rose, after the delivery there was no difference between groups. The plasma ACTH prior to the delivery was at the same level in all subjects, during the third stage of labour ACTH rose in the both groups, but was statistically higher in group with oxytocin infusion. The concentrations of cortisol before delivery was similar in both groups, then rose to the same level during the delivery and then declined to the level observed before delivery. The DHEA concentration was similar in both groups, did not change during the labour, there was no difference between its level in the umbilical vein and artery. In the group with oxytocin-induction there was no correlation between maternal CRH and ACTH or cortisol concentration, but such a correlation occurred in the group with elective cesarean section. The concentration of ACTH and DHEA in umbilical artery was similar in both groups but the concentrations of CRH and cortisol in umbilical artery in group of newborns delivered after elective cesarean section were statistically higher. CONCLUSION The activity of the mother's HPA axis is partially inhibited rather by psychological stressors, than events connected with mode of parturition. The newborn's HPA axis responds in a specific way to mother's HPA-axis. The communication between mother's and newborn's HPA is possibly related to many other factors than placental CRH and ACTH. It is necessary to consider effects of central CRH and ACTH on the fine-tune regulation of HPA axis in the late pregnancy and parturition, not detectable due to the high levels of placental hormones.