Objective: To investigate the effect of route of delivery on the antioxidant system of newborns. Methods: We used the cord blood taken during labor of 56 vaginal deliveries and 50 elective cesarean sections. The specimens were analyzed for the plasma malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glucose 6-phosphate dehydrogenase (G6PD) activity and leukocyte count. Results: SOD and CAT activities were significantly higher in the elective cesarean group than the vaginal delivery group (p < 0.01 and p < 0.005, respectively), but G6PD activity was similar between the groups. Plasma MDA level was lower in the cesarean group compared to the vaginal delivery group (p < 0.001). Leukocyte count was higher in the vaginal delivery group (p < 0.005). Conclusion: Our findings suggest that the route of delivery has an effect on oxidative stress in newborns exposed to oxidative stress during delivery. It can be suggested that the antioxidant system works more efficiently to overcome oxidative stress in newborns delivered via cesarean section. Copyright (c) 2005 S. Karger AG, Basel.