Exercise During Pregnancy

An active lifestyle promotes health. Regular physical exercise improves mood, builds bones and muscles, gives us energy, and helps us live longer. Because these benefits apply to everyone, including pregnant women, I generally encourage my obstetric patients to be active during their pregnancies.

While participation in a wide range of physical activities is safe during pregnancy, some changes in exercise patterns will probably be necessary. As the baby grows and the pregnant woman's posture changes, strain on the low back and leg joints increases. If pain during exercise occurs, that activity should be discontinued or modified to avoid injury.

Some women with medical or pregnancy complications should not exercise. Exercise during pregnancy is unsafe for women with the following conditions:

  • severe heart or lung disease
  • premature labor
  • vaginal bleeding in the third trimester
  • pregnancy-induced hypertension

In order to derive health benefits from exercise, all individuals should perform at least thirty minutes of moderate physical exertion daily, five or more days per week. Healthy women with normal pregnancies also should follow this recommendation. The thirty minutes of exercise need not be continuous; the same health benefits are achieved from several shorter activity sessions throughout the day.

"Moderate" exercise is any activity that is equivalent in difficulty to brisk walking. Heart rate monitoring is not necessary or very useful for guiding your pace. Instead exercise should be self-paced so that you are breathing harder than normal but still are able to carry on a conversation. A woman is exercising too hard and should stop if she experiences chest pain, breathlessness, lightheadedness, or uterine contractions.  Pregnant women who have not been regular exercisers can begin an exercise program during pregnancy. Women who develop diabetes during pregnancy will be advised to exercise because exercise has been shown to help control blood sugars. A simple way to start exercising is to walk. First, simply walk as far as you can comfortably: this is your baseline. It may be only five minutes—that is okay. Make sure you are walking at a speed and length of time you can easily tolerate. Then try to increase the baseline distance by ten percent every one or two weeks. After you are walking thirty or forty minutes each day, walk a little farther in the same time. If you can do this, you will have increased the intensity of your exercise. The goal is to develop a habit of regular physical activity at a level that is right for you.

Certain activities and sports deserve special consideration in pregnancy. The safety of each activity is largely determined by the specific movements required by that activity. After twenty weeks of pregnancy, women should not do exercises that require lying flat on the back, because this position interferes with the heart's ability to pump blood. Motionless standing can also interfere with blood circulation and should be avoided.

Weight lifting and strength training are safe and effective in pregnancy if low weights (less than fifteen pounds) are used. Heavy weight lifting which causes the lifter to bear down and strain should be avoided.

Excellent exercises for pregnant women include walking, stationary biking, and swimming. Water exercise during pregnancy may be the best form of exercise for pregnant women for several reasons:

  • minimal stress on joints
  • water prevents overheating
  • balance and falling are not issues

Exertion at altitudes of up to 6,000 feet is safe during pregnancy. Because less oxygen is available at altitude, an acclimatization period of one or two days is recommended, and high intensity exercise should be avoided. All women active at these altitudes should be aware of the signs of altitude sickness: headache, poor sleep, anorexia, fatigue, nausea, and vomiting. If these symptoms occur, stop exercising, return to a lower altitude, and seek medical attention.

The competitive athlete may continue to train during pregnancy. However, due to the inevitable changes her body will undergo, her competitive ability will decline as her pregnancy progresses. Nevertheless, most elite athletes want to train as hard as possible during pregnancy so they can return to competition as soon as possible after delivery.

Though there have been no reports of stillbirth related to maternal exercise, an upper limit of safe exercise duration and intensity has not been established. Two issues should be kept in mind:

  • Heat stress. There is evidence that increasing a woman's body temperature in the first trimester may cause birth defects. This was seen in women who were in hot tubs or saunas and has not been reported in conjunction with exercise. Nevertheless, since exercise raises body temperature, pregnant women should take steps to avoid overheating. Pregnant women should exercise in cool weather or indoors with air-conditioning and should stay well-hydrated. Hydration is monitored by weighing before and after an exercise session. Any weight loss is fluid loss that should be replenished before exercising again. One pound weight loss roughly equals one pint fluid.
  • Caloric costs. Pregnancy requires 300 extra calories per day. These requirements are higher when more energy is spent each day through exercise. Pregnant athletes should be monitored closely to insure they are gaining weight appropriately.

Many physical changes of pregnancy continue for four to six weeks after delivery. Prepregnancy exercise routines may be resumed gradually as the woman is physically able. Competitive athletes tend to resume training quickly after delivery. There is no evidence that rapid resumption of training after delivery is harmful to women. There is evidence, however, that exercising after delivery helps prevent postpartum depression. Women who delivered by Cesarean section should avoid heavy lifting for several weeks after delivery.

In summary, healthy women with normal pregnancies can and should exercise during pregnancy. A woman’s body changes during pregnancy. Though she will need to modify her usual routine, she can remain fit or even improve her fitness during pregnancy. Exercise clearly benefits pregnant women and does not jeopardize the unborn baby.

Dr. Glynn M. Wittber is a physician specializing in Obstetrics and Gynecology with The Jackson Clinic. She is Board Certified by the American Board of Obstetrics and Gynecology. After graduating from Vanderbilt University with a degree in Molecular Biology, she received her medical degree from the University of Tennessee College of Medicine, Memphis and completed her internship and residency at The Ohio State University Hospitals in Columbus, Ohio.