Stress of delivery and plasma endorphins and catecholamines in the newborn infant.

Cord plasma levels of endorphins and catecholamines were correlated with the values of cord blood gas analysis and with hemodynamic parameters in 11 newborns (group A) delivered by elective cesarean section and in 18 newborns (group B) born spontaneously by vaginal route. All infants were in a good condition. No statistically significant differences were found in the mean cord plasma levels of adrenaline (A), noradrenaline (NA) and immunoreactive beta-endorphin (ir beta-E) between groups A and B. After spontaneous labor in group B a highly significant negative correlation was found between plasma NA level and pH and a positive correlation between NA and carbon dioxide tension in cord arterial blood and between NA and the short-term variability of the fetal heart rate before birth. Cord plasma A and ir beta-E did not show such correlations. These findings show that cord plasma level of NA is a sensitive indicator of minor stress during normal labor. After birth, during the first two hours of life, the mean plasma level of ir beta-E decreased in group B after vaginal delivery, but remained at a higher level in group A after elective cesarean section. This shows that the mode of delivery influences the neonatal endorphin secretion.