Maternal and fetal beta-endorphin release in response to the stress of labor and delivery.

Overview

In order to clarify the stress effect of labor on maternal and neonatal plasma levels of beta-endorphin, we measured this peptide in samples taken from 40 pregnant patients and their neonates at the time of normal vaginal delivery (n = 15), and at cesarean section performed either in early labor (n = 13) or prior to labor (n = 12). The mean (+/- SE) maternal plasma concentration of beta-endorphin in the vaginal delivery group was 40.3 +/- 5.6 fmol/ml, which was significantly higher than that in their neonates (21.3 +/- 2.9 fmol/ml). In contrast, maternal levels of beta-endorphin in the cesarean section groups (8.2 +/- 1.2 and 8.5 +/- fmol/ml) were significantly lower than those in their neonates (23.3 +/- 5.6 and 15.6 +/- 2.8 fmol/ml). Concentrations of beta-endorphin in mothers delivered vaginally were also significantly higher than those in mothers delivered by cesarean section. However, there was no difference in mean cord levels of beta-endorphin among the three groups. These findings indicate that neither the presence or absence of labor affects fetal plasma beta-endorphin secretion and the stress of labor and delivery produces a marked increase in maternal release of beta-endorphin.