The effect of labor on maternal and fetal circulating catecholamines.

Maternal circulating catecholamines were determined in nonpregnant (n = 15) and antepartum (n = 15) subjects and at spontaneous vaginal (n = 20) and repeat cesarean section (n = 20) deliveries. Newborn levels of catecholamines were determined prior to the onset of respiration in the vaginal delivery (n = 20) and cesarean section (n = 20) groups. Maternal levels of norepinephrine at 36 to 38 weeks' gestation were lower than values in nonpregnant individuals, and did not increase at cesarean section but rose to nonpregnant levels at vaginal delivery. Antepartum levels of epinephrine were lower than levels in nonpregnant subjects and rose above nonpregnant levels in both delivery groups (P less than 0.02). Maternal levels of dopamine followed a similar pregnancy decline and rose above nonpregnant levels at delivery in both groups (P less than 0.02). Maternal levels of dopamine in the cesarean section group were significantly higher than those in vaginal delivery (P less than 0.05). Newborn levels of catecholamines demonstrated significant newborn secretion of norepinephrine, epinephrine, and dopamine at delivery in both groups. Umbilical arterial levels of norepinephrine and epinephrine were significantly greater after vaginal delivery than those after abdominal delivery (P less than 0.01). The significance of circulating catecholamines to, and their possible roles in, the parturient women and fetus are discussed.