Continuing an exercise program during pregnancy provides many benefits. It can increase a woman’s overall comfort during pregnancy and may protect against leg cramps, thrombosis and varicose veins. It will improve muscle tone, strength, overall balance and coordination, as well as a woman’s general energy level and feeling of well being. There will be a quicker and easier return to pre-pregnancy weight and fitness level as well.

Scientific studies have shown that exercise in pregnancy is associated with less overall weight gain and slightly smaller babies compared to women who do not exercise while pregnant. Exercising women tolerate labor and delivery better than non-exercising women.

Exercise in pregnancy is safe, as long as one modifies their previous exercise patterns to conform to the guidelines set forth by the American College of Obstetrics and Gynecology.

Special Considerations in Pregnancy

As we exert ourselves physically, in order to meet the increased demands of oxygen and fuel for the working muscles of the body, the cardiac output (amount of blood the heart pumps per unit of time) increases. The heart does this by pumping faster and by squeezing out more blood per heartbeat. That is why with exercise, the heart rate increases.

Because pregnancy is already a high-output cardiac state to begin with, an increase in heart rate during exercise can only keep up with the increased demand for more tissue oxygen at mild to moderate degrees of exertion. With very strenuous or prolonged degrees of exertion the heart cannot pump out enough oxygen to meet the total body need. This can result in decrease in blood flow to the uterus (and, thus, the placenta and fetus), depriving the fetus of adequate oxygen for varying periods of time. Only with strenuous or prolonged exertion is there a risk for this degree of reduced blood flow to the uterus.

In pregnancy, a constant supply of blood glucose (the body’s primary sugar and energy source) is very important for the growing fetus. Because glucose is so readily available in pregnancy, it serves as the primary fuel used with even mild and moderate physical exertion. With more prolonged or strenuous exertion the glucose supply can be depleted, thus, endangering the fetus. As pregnancy advances, maternal weight increase and even the same type and degree of exercise will require more oxygen and energy, further limiting the safe degree of exertion to be recommended. This is especially true for weight-bearing exercise (walking, jogging), as the body must work harder to propel the extra weight as it exerts itself. Thus, the intensity of such exercise must be decreased as pregnancy advances.

Because excess heat has been implicated as a possible cause of birth defects, exercise should take place in a well-ventilated area and care should be taken not to overheat, especially in the first trimester. Limiting length and duration of exercise, wearing loose, comfortable clothing, drinking fluid and stopping if feeling very warm are simple and straightforward measures that can be taken to maintain a core temperature of less than 100 degrees. If it is hot or humid, don’t work out and remember not to exhaust yourself.

Near the fourth month of pregnancy, no exercise, lying flat on your back should be done as this may interfere with the return of blood to your heart. As a woman’s center of gravity is higher and slightly more forward during pregnancy, a woman may feel unstable as pregnancy progresses and may be more prone to lose her balance. Thus, it is important to exercise in a safe environment (well lit, well ventilated, safe equipment that you are already comfortable with and in a non-isolated place.)

In summary, due to pregnancy considerations, only moderate exercise should be done, with one to two minutes of lower intensity activity every 10 minutes. Warm up and cool down periods are important and staying well hydrated is key!

Exercise Options

Contact sports are not recommended in pregnancy. Sports putting you at risk for falling like skiing and horseback riding should also be avoided. Scuba diving, skydiving, and high altitude mountain climbing are also not recommended in pregnancy.

The best exercise options for the pregnant patient are brisk walking, swimming or water aerobics. Exercise machines that a woman has used previously are a good choice, including treadmills for walking and limited jogging during the first four to five months of pregnancy. Stationary bikes are also a good alternative as they limit the impact on joints, which undergo changes in pregnancy. Calisthenics, yoga, cycling, aerobic classes are also reasonable options.

Who Should Not Exercise in Pregnancy?

Women who have not been physically active prior to pregnancy should not start a fitness program during pregnancy other than limited walking or other low intensity exercise, and, only after discussing this with their physician. If a woman has health problems, a history of poor pregnancy outcome or a high-risk pregnancy, she should also discuss physical activity with her physician.

If you are pregnant and have any of the following conditions, you should not exercise during the pregnancy:

• Preeclampsia
• Premature rupture of the membranes
• Preterm labor symptoms during the prior or current pregnancy
• Incompetent cervix or a cerclage in place
• Poor fetal growth
• Placenta previa
• Twins or greater after the second trimester

Women with other medical or obstetrical conditions may need to avoid exercise as well.