Naloxone and its possible relationship to fetal endorphin levels and fetal distress.

This case report of fetal asphyxia and related studies suggest that fetal endorphins play a role in fetal pain tolerance and cardiovascular asphyctic responses. Elevated fetal endorphin levels may, like narcotics, produce abnormally "flat" fetal heart rate patterns intrapartum and fetal tolerance to pain. Although naloxone hydrochloride was used with some success to return flat fetal heart rate patterns to "normal," the unopposed antagonism of fetal endorphins by naloxone in times of fetal distress may be detrimental.