Concentration of beta-endorphin in relation to the mode of delivery and anesthesia was studied in maternal and umbilical cord plasma in 30 healthy women at term pregnancy. At elective cesarean section under epidural anesthesia, the mean maternal beta-endorphin level rose from 9.8 +/- 2.7 pmol/L (SE) before induction to 15.5 +/- 3.7 pmol/L at the time of delivery (P less than .02). Under general anesthesia the mean beta-endorphin level increased more, from 14.6 +/- 7.2 to 34.4 +/- 7.8 pmol/L (P less than .02), reaching the mean beta-endorphin value of the second stage of normal labor, 39.4 +/- 7.0 pmol/L. In the cord arterial and venous plasma, the mean beta-endorphin value was significantly higher after spontaneous labor (40.9 +/- 11 and 40.1 +/- 9.2 pmol/L, respectively) than at elective cesarean section under epidural (14.3 +/- 1.9 and 12.4 +/- 3.6 pmol/L, respectively) or general anesthesia (11.9 +/- 2.2 and 13.4 +/- 2.2 pmol/L, respectively).
Thus cesarean section under general anesthesia proved to be more stressful for the mother than that under epidural anesthesia, when beta-endorphin release is used as the measure of stress. The mode of anesthesia did not seem to influence the plasma beta-endorphin level in the newborn infant. Normal delivery by vaginal route increased the release of beta-endorphin both to the maternal and the fetoplacental circulation.
[…] as far as I know, beta-endorphin has not been measured in earlier colostrum (maybe they can’t get enough of a sample to analyse), but it is well known to be elevated in newborn and mother according to mode of delivery - see below. Zanardo et al show that these elevated levels can cross into the breastmilk, indeed are probably actively transported because in their study, colostral levels are double maternal levels.
Beta-endorphin is a stress hormone, and its release in labour is thought to be related to the ’stress’ of labour for mother and baby, paralleling the other stress hormones such as adrenaline/noradrenaline as well as corticosteroids, in fact B-E is thought to enhance corticosteroid release. Zanardo et al comment that the elevated levels in colostrum may be "… of importance in the postnatal development of several related biological functions of newborn infants, including endocrine amd immune response."
Sarah J Buckley GP/family physician, mother, author of Gentle Birth, Gentle Mothering: The wisdom and science of gentle choices in pregnancy, birth, and parenting www.sarahjbuckley.com
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