It is important to check with your doctor before continuing or starting an exercise program during pregnancy. Your doctor will base his or her recommendation on your general health and current fitness level. Overheating during the first trimester can impair development of the baby's central nervous system. Don't exercise in hot, humid weather or when you have a fever, and forego saunas and hot tubs, too. Keep a moderate pace.
Prolonged exercise can divert oxygen in the blood away from the baby.
Drink plenty of fluids. Have beverages before, during, and after exercise. Because your ligaments are more lax during pregnancy, sports injuries are a real concern. Avoid jumping and jarring motions, along with activities that require rapid changes in direction. Make sure your footwear fits properly and provides good traction.