Yes. Exercise is safe during pregnancy and should not be avoided. However, there are a few considerations that need to be kept in mind. Your center of balance is constantly changing and you will need to be more careful with physical activity. Also, prolonged periods of time standing should be avoided. As your uterus grows, it will place more pressure on the large blood vessels that leave and enter your heart. The best activity for pregnant women is swimming. Other good activities for pregnant women include walking and stationary biking. Exercise reduces such discomforts as backache, constipation, fatigue and bloating. Exercise promotes muscle tone, strength, and endurance.