Investigation of the teratogenic effects of exercise on pregnancy outcome in mice

Swiss Webster female mice were arbitrarily assigned to a heavily exercised group (HE), a moderately exercised group (ME), or a sedentary group (S). Exercised groups were subjected to a progressive treadmill training routine, 6 days a week (60 min per day) for a total of 9 wk. Following mating after 6 wk of training, treatment groups continued to exercise at preconceptual intensities. Pregnant mice were sacrificed on the 19th day of pregnancy, and the fetuses were recovered. A positive training effect was demonstrated by a significant increase in succinate dehydrogenase activity in the gastrocnemius muscles of exercising dams. The numbers of implants, resorptions, live fetuses, mean fetal weight, and developmental stage were unaffected by the exercise treatment. A detailed fetal examination revealed no significant skeletal or gross tissue abnormalities in any of the experimental groups.