Endogenous opioid peptides in intrapartum uterine blood

Endogenous opioid peptides have consistently been reported to exert significant influence on several parameters of reproductive physiology, including tolerance to pain, release of prolactin, pleasurable behavior patterns, and appetite satiety. Immunoreactive endorphins measured in several hundred samples of postpartum uterine blood had a mean value of 190 pg/ml and a range of 60 to 520 pg/ml. Individual values in 100 mothers who were delivered at the Northwest Hospital failed to correlate with doses of postpartum pain medications, infant feeding patterns, and recorded estimates of maternal bonding behavior. Postpartum "blues" may be related to stress-induced depletion of endorphinergic systems.