Free radical production and high catecholamine levels are implicated in the modulation of Na(+), K(+)-ATPase, and Mg(2+)-ATPase activities. The aim of this study was to investigate the effect of the mode of delivery on the above-mentioned enzyme activities in maternal-neonatal erythrocyte membrane. Women with normal pregnancy (N = 30) were divided into two groups: Group A (N = 16) with normal labor and vaginal delivery, and Group B (N = 14) with scheduled cesarean section; 20 non-pregnant women were the controls. Blood was obtained from controls and mothers, pre- versus post-delivery, and from the umbilical cord (CB). Total antioxidant status (TAS), membrane enzyme activities, and catecholamine blood levels were measured with a commercial kit, spectrophotometrically, and by HPLC methods, respectively. The results showed that: TAS levels, catecholamine, and the membrane enzyme activities were similar in the two groups of mothers pre-delivery, whereas both enzyme activities were lower than those of controls. TAS levels were reduced whereas Na(+), K(+)-ATPase activities (0.35 +/- 0.03 vs. 0.65 +/- 0.06 micromol Pi/h x mg protein, P < 0.001), and catecholamine levels were increased post-delivery in mothers of Group A and unaltered in Group B (0.38 +/- 0.02 vs. 0.40 +/- 0.03 micromol Pi/h x mg protein, P > 0.05), at the same times of study. Mg(2+)-ATPase activities remained unaltered in both groups of mothers and newborns. Na(+), K(+)-ATPase activity was similarly lower in the CB of neonates than those of their mothers, pre-delivery. Our results suggest that: (a) during a normal vaginal delivery process, the low TAS and the increased levels of catecholamines may increase Na(+), K(+)-ATPase activity, post-delivery; (b) the low enzyme activities evaluated in mothers pre-delivery may be due to the high estrogen levels and those in newborns due to perinatal immaturity.