Maternal Total β-Endorphin Immunoreactivity During Labor and Delivery

Circulating plasma β-endorphin (BIR) levels underestimate the BIR levels in the blood. To determine the effect of epidural anesthesia on BIR, we measured total blood (plasma + erythrocytes) BIR during labor and delivery (19 epidural, 6 control patients). Total BIR levels seem to predict the anesthetic need in patients during labor. Acute changes in the pain status in patients were better predicted by the plasma than the total BIR activity.