How Pregnancy Affects Exercise

Even if you're a seasoned athlete, your body will react differently to exercise when you are pregnant. Watch for these changes:

• Balance fails after 20 weeks as your abdomen throws off your center of gravity, making you more susceptible to falls. This is something to remember if you participate in activities such as jogging or tennis.
• As the growing uterus crowds the lungs, you'll find that you lose your breath much sooner during exercise. Working out harder and longer won't change this fact.
• Your heart naturally beats faster during pregnancy. This means you won't have to exercise as vigorously to reach your target rate. It also means you can overdo it very easily.
• Blood volume increases during pregnancy, but more blood is channeled to internal organs (such as the uterus) and less to the muscles. This can make muscles tire more quickly.
• The hormone called relaxin relaxes the pelvic joints in preparation for childbirth; it also loosens all ligaments and joints making you more prone to sprains and falls.

Another thing that can change the way you exercise during pregnancy is increased blood flow and a higher metabolic rate. This means you'll feel warmer than usual when you exercise and might become overheated sooner than you expect. This can be dangerous. Some animal studies suggest that overheating can cause birth defects. To be on the safe side, the American College of Obstetricians and Gynecologists (ACOG) cautions against overheating through exercise, especially in the first trimester. To test yourself, take your temperature by placing a thermometer under your armpit when you finish exercising. It should not be higher than 101°F.

To keep from overheating, the American College of Sports Medicine makes the following recommendations:

• Drink about 16 ounces of water or a sports drink two hours before you begin exercising.
• During your workout, drink 5 to 12 ounces every 15 to 20 minutes.
• Weigh yourself before and after exercise and drink two more glasses of water for every pound you've lost.

You can see that exercise during pregnancy is not the same as before. Because your body reacts differently to physical exertion now, you have to be more mindful of how exercise affects not only you, but your baby as well.