Pain and plasma beta-endorphin level during labor.

Plasma concentration of beta-endorphin was observed during labor in 16 women and correlated with pain assessed subjectively using pain scores. Ten women did not receive any medication during the follow-up. A concomitant increase in pain score and plasma beta-endorphin level was found with advancing labor. In the remaining six women, epidural anesthesia was used to relieve pain. During epidural anesthesia, plasma beta-endorphin levels and pain scores decreased concomitantly. The same effect was found after a repeated dose of the anesthetic. These findings showed a correlation between pain and the secretion of beta-endorphin during labor, but the mode of action of beta-endorphin remains unsolved.