A good rule is to avoid overheating or getting out of breath. A variety of changes occur to a woman's body when pregnant. Regular exercise that is done as a pregnancy develops can benefit those changes. As the uterus grows bigger, the body's center of gravity changes, making it easier for the pregnant woman to lose her balance. Exercise helps the individual easily adapt to her changing shape.
Normal hormone changes cause ligaments and joints to relax.
This increases the chance of sprains. Strength and flexibility decrease the risk of straining a muscle or joint. Because of the extra effort your heart makes during pregnancy, it beats faster. Even moderate exercise can make your heart stronger. During exercise, keep your heart rate lower than 140 beats per minute.