As your abdomen increases in size, your posture will shift forward, putting new strain on your back muscles and changing your balance. Toward the end of your pregnancy the joints and ligaments in your pelvis will loosen in preparation for labor. All of these changes will affect the way your body responds to exercise. For example, muscle and joint injuries are more likely to occur if you're not careful. Sports to avoid It's best to avoid certain sports altogether while you're pregnant.
Snorkeling is a safer alternative.
After the first trimester, avoid floor exercises that require you to be on your back for a prolonged time. Getting started If you're not now exercising regularly, it's best to begin modestly and gradually increase the frequency and length of each session. Your goal should be three or four 20-minute sessions weekly. Allow three or four weeks to work up to this goal. Walking is an outstanding exercise to start with.