Be sure to talk to your physician before starting or continuing an exercise program. Exercise during pregnancy has many benefits and there are a variety of exercises to do that are safe. You also need to make sure you get plenty of rest (at least seven to nine hours each night). It is also important to know your limits. Exercise can help you have more energy, tone muscles needed for delivery, improve your posture, strengthen your heart and lungs, lower stress and prevent excess weight gain. You can do brisk walking, swimming, biking (wear safety gear), take an exercise or yoga class. Avoid activities where the risk of hurting your belly or falling is high. If you aren't accustomed to regular exercise, start slowly. If you exercised regularly before pregnancy, you may need to adjust your routine to accommodate the changes. Once you are 24 weeks you need to start limiting your high impact exercises. Stop exercising and call your physician right away if you feel pain, have vaginal bleeding or discharge, feel dizzy or faint, feel short of breath, have an irregular heart rate or if your heart beats very fast, have trouble walking, have back or pelvic pain, or notice any other unusual symptoms.