There are numerous benefits to pregnant women of remaining active during pregnancy. These include improved weight control and maintenance of fitness. There may also be benefits in terms of reduced risk of development of gestational diabetes meilitus and improved psychological functioning. Moderate intensity aerobic exercise has been shown to be safe in pregnancy, with a number of studies now indicating that for trained athletes it may be possible to exercise at a higher level than is currently recommended by the American College of Obstetricians and Gynecologists. Studies of resistance training, incorporating moderate weights and avoiding maximal isometnc contractions, have shown no adverse outcomes. There may be benefits of increased strength and flexibility. The risk of neural tube defects due to exercise-induced hyperthermia that is suggested by animal studies is less likely in women, because of more effective mechanisms of heat dissipation in humans. There is accumulating evidence to suggest that participation in moderate intensity exercise throughout pregnancy may enhance birth weight, while more severe or frequent exercise, maintained for longer into the pregnancy: may result in lighter babies. There have been no reports of foetal injury or death in relation to trauma or contact during sporting activities. Despite this, a risk of severe blunt trauma is present in some sporting situations as pregnancy progresses. Exercise and lactation are compatible in the post-partum period, providing adequate calories are consumed. Considerations of pelvic floor function and type of delivery are relevant in planning a return to certain types of exercise at this time.