Exercise at high altitudes should be done with caution since information is limited as to the safety. However, there have been no reports of injury, pregnancy complications, or losses associated with low-intensity exercise such as skiing, running, hiking, or mountain biking at moderate altitude. Less information is available about the safety of exercise around the time of conception. Exercise at various levels of intensity help to improve the mother's feeling of well being and level of fitness. Exercise also improves cardiovascular function as seen in increased cardiac output that continues into the postpartum period.
Exercise also affects maternal weight gain and postpartum weight loss.
Those who exercise during pregnancy and continue afterwards are more successful at returning to their pre-pregnancy weight and fitness level. There also seems to be a relationship between exercise and easier, less complicated labor. Compared to babies of sedentary mothers, those born to moms who exercised during pregnancy are leaner and seem to have a greater tolerance to the stresses of late pregnancy, labor, and delivery. Babies of the exercising mothers were heavier and longer than the control babies, although maternal weight gain was similar. Other findings from the study suggest that exercise stimulates growth of the placenta that, in turn, may enhance fetal growth through increased delivery of nutrients.