[Management of regular exercise in pregnant women]

In recent years with ever-increasing numbers of pregnant women wanting to participate in sport activities, the question as to how safe maternal exercise is for mother and fetus has become more important. The effects of pregnancy on maternal cardio-respiratory system include increases in oxygen consumption, cardiac output, heart rate, stroke volume, and plasma volume. The increase in oxygen reserve seen in early pregnancy is reduced later, suggesting that maternal exercise may present a greater physiological stress in the third trimester. The aims of this article are 1) to comment on the evidence relating to the health risks and benefits of physical activity for pregnant women and their unborn fetuses and 2) to realize guidelines for management of maternal exercise. In the absence of either obstetric or medical complications, pregnant women can continue to exercise and derive related benefits. The type, intensity, frequency, and duration of the exercise seem to be important determinants of its beneficial effects. Evidence suggests that weight-bearing exercise produces a greater decrease in oxygen reserve than non weight-bearing exercise. Furthermore, to maintain a heart rate below 150 beats per minute during pregnancy, the intensity of weight-bearing exercise must be reduced. In addition, depending on the individual's needs and the physiologic changes associated with pregnancy, women may have to modify their specific exercise regimens. Although increases in the frequency of uterine contractions have been observed during physical activities, changes are often minimal. In response to moderate exercise, the increase in frequency of uterine contractions is gestation dependent and significant in the third but not in the second trimester. The physiological adaptations to exercise during pregnancy appear to protect the fetus from potential harm and, while an upper level of safe activity has not been established, the benefits of continuing to be active during pregnancy appear to outweigh any potential risks. All decisions about participation in physical activity during pregnancy should however be made by women in consultation with their medical advisers.