Plasma beta-endorphin concentration in depressed newborns at term

Objective: The concentration of beta-endorphin in umbilical arterial blood was related to plasma acid-base parameters, type of acidosis, and neonatal health immediately after delivery, to reveal whether fetal acidosis and later, neonatal depression, were associated with elevated levels of beta-endorphin. Methods: Twenty-six, vaginally delivered infants, chosen at random, were studied. In 11 of 26 (42.3%) umbilical artery pH was under 7.20 and 6 of 26 (23.1%) were considered as having signs of neonatal depression, defined as a need for additional oxygenation because of decreased respiratory drive at least during the first day of life. Arterial cord blood samples were collected at delivery for acid-base and beta-endorphin determinations. Neonatal acidosis, if present, was classified furher as metabolic, respiratory, or mixed. Conclusions: Plasma beta-endorphin concentration in newborn umbilical artery at delivery might be considered as a consequence of fetal stress reaction during labor, with elevated levels in acidosis. It could be speculated that high beta-endorphin levels might prevent acidotic infants from getting rid of excess carbon dioxide, thus causing neonatal respiratory depression,