Endothelial dysfunction of the maternal vasculature induced by pro-oxidants may contribute to the development of preeclampsia. Obesity results in vascular inflammation and oxidative stress and is therefore a risk factor for preeclampsia. Regular exercise is known to induce antioxidants. We recently demonstrated that stretchers (subjects who performed low-intensity exercises) had a lower incidence of preeclampsia as opposed to walkers (moderate-intensity exercise; 2.6% versus 14.6%). We now seek to determine the possible protective mechanisms. We hypothesized that stretchers will have higher vascular levels of the antioxidant superoxide dismutase (SOD) and plasma transferrin levels, an antioxidant marker. We conducted immunohistochemical analyses of blood vessels embedded in fat biopsy samples obtained during cesarean sections from women who were randomized to either stretching ( N = 6) or walking ( N = 5) exercises. In addition, levels of plasma transferrin were measured. SOD expression was increased ( P < 0.05) in stretchers [106.3 (interquartile range 84.2 to 127.8 arbitrary units (AU)] when compared with that of walkers [56.92 (interquartile range 46.35 to 82.32 AU)]. Transferrin levels continued to increase throughout gestation only among the stretchers. There appears to be a higher antioxidant protective effect in subjects who performed low-intensity exercise during pregnancy. © Thieme Medical Publishers.