Maternal and umbilical venous plasma immunoreactive beta-endorphin levels during labor with and without epidural analgesia.

Maternal and umbilical venous plasma immunoreactive beta-lipotropin/beta-endorphin levels were determined during labor in 23 healthy parturient women at term. Eleven of the mothers received a segmental epidural analgesic for relief of pain, whereas the other 12 mothers were nearly pain-free and needed no analgesia. Maternal immunoreactive beta-lipotropin/beta-endorphin levels were already significantly elevated at the beginning of labor in both groups in comparison with nonpregnant young women. Maximum levels of immunoreactive beta-lipotropin/beta-endorphin were reached at delivery, and these mean levels were significantly higher than the initial mean levels in the epidural group (p less than 0.05) and in the control group (p less than 0.001). There were statistically no significant differences between the groups at any time. The umbilical venous plasma immunoreactive beta-lipotropin/beta-endorphin levels did not differ from each other in the epidural and the control groups. These results suggest that the stress of labor causes an increase in the maternal secretion of immunoreactive beta-lipotropin/beta-endorphin which is not related to the degree of pain itself. Epidural analgesia has also no effect on umbilical venous plasma immunoreactive beta-lipotropin/beta-endorphin.