The guidelines and attitudes about exercise during pregnancy have changed considerably through the years. Previous guidelines allowed a woman to walk one mile a day, ideally broken up throughout the day. Then the 140 beats per minute (BPM) limit guideline was instituted. While our knowledge of this particular area of exercise physiology is still incomplete, we now know a lot more about the benefits and risks of exercising during pregnancy. As a result, much more specific guidelines have been established.
Pregnancy Exercise Benefits
- Decreased risk of gestational diabetes & long-term obesity
- Control of gestational diabetes
- Improved energy levels
- Improved posture
- Improved muscle tone, strength, & endurance
- Possible faster delivery
- Enhanced recovery from childbirth
- Reduced backaches
- Reduced bloating & swelling
It’s important for the mother to understand that this is a time in her life to maintain health & fitness and achieve the benefits that exercise has to offer during pregnancy. Training to make significant improvements in fitness and performance should be avoided until postpartum due to the risks and many changes that occur during pregnancy.
The amount of weight a woman should gain during her pregnancy is largely determined by what her current weight was prior to becoming pregnant. Excess weight gain and failure to lose this weight six months postpartum are predictors of long-term obesity.
- Normal weight prior to pregnancy: 25-32 lbs.
- Overweight prior to pregnancy: 15 lbs.
- Underweight prior to pregnancy: 40 lbs.
Physician approval for exercise is always required prior to continuing or starting an exercise program. Risks for the mother include hypoglycemia (low blood sugar), fatigue, and musculoskeletal injuries. The baby is at risk for hyperthermia (overheating) and decreased uterine blood flow. The mother should stop exercising before fatigue sets in and follow the recommended guidelines for exercise mode, frequency, intensity, and duration. Should any of the following warning signs occur, exercise should be discontinued the mother should consult her physician.
Exercise Warning Signs During Pregnancy
Shortness of breath prior to exercise
Calf pain or swelling
Decreased Fetal Movement
Amniotic Fluid Leakage
Some pregnant women should not exercise. Women that have cardiac disease or restrictive lung disease may not be able to exercise. Pregnancy-induced hypertension, an incompetent cervix, intrauterine growth retardation, second and third trimester bleeding, and premature rupture of membranes are conditions that will deem exercise inappropriate.
Walking, stationary cycling and swimming are popular exercise modes for pregnant women. Women who were participating in resistance training prior to pregnancy should continue to do so. Light to moderate weights with high repetitions should be used (e.g.- 12-15 reps) to maintain muscle function while preventing excessive stress on ligaments and joints. It is recommended that women who were not engaging in resistance training prior to pregnancy wait until postpartum to begin.
Activities such as racquet sports, basketball, and softball should be avoided because they can increase the strain on muscles, tendons, and ligaments, and may also pose a risk to the baby (e.g.- ball hitting the abdomen). For many of the same reasons, all high-impact activities should be avoided. Stretching should be gentle and static to maintain joint flexibility. Ligaments and joints become more lax and mobile during pregnancy due to hormonal changes, so aggressive stretching should be avoided.
In the second trimester, the supine position (on your back) should be avoided at this time. The mother gains an average of one-two pounds per week during the second trimester. Due to the increased weight of the baby, this position can compress the vena cava and inhibit oxygen & blood flow to the baby. During the third trimester, aerobic exercise may need to be limited to stationary equipment, walking, and swimming due to alterations in the center of gravity and balance. Limiting resistance training to selectorized machine use is recommended once center of gravity and balance has been altered.
Exercising three-four times per week is recommended for pregnant women. Recent research indicates that women who exercise five or more times per week have substantially increased odds for a low birth weight baby. Pregnant women who exercised two or fewer times per week have modestly increased odds for a low birth weight baby.
Past guidelines called for 140 BPM as the maximum exercise heart rate during pregnancy. While this is a good general guide for the average age of a pregnant woman performing moderate intensity exercise, it does have some limitations. It doesn’t take into consideration those who have been exercising prior to becoming pregnant. A pregnant woman who was exercising prior to being pregnant would likely tolerate a higher exercise intensity better than someone who was previously sedentary. It also doesn’t take into consideration the large variations in age. There would be a significant difference in exercise heart rate between a 19-year-old pregnant girl and a 40-year-old pregnant woman. The primary concern with exercise intensity during pregnancy is blood flow to the baby. With increasing exercise intensity, increased blood flow to the working muscles could decrease blood flow to the baby and in turn, oxygen levels. An appropriate guide to use is a fairly light to somewhat hard rate of perceived exertion. The mother should be able to talk while exercising (known as the talk test).
The standard recommended exercise duration during pregnancy is 30-40 minutes. However, on some days, fatigue may occur earlier than others. The duration of the session should be determined by how the mother feels that day. During the first trimester, when the baby’s major systems are beginning to form, fatigue is very common. Although most women can exercise at this time, it is important to stop exercising before excessive fatigue sets in. Energy levels typically increase during the second trimester but the duration guidelines should still be adhered to.
At least 300 additional calories per day are required for exercise during pregnancy to supply the mother will additional energy and avoid compromising the growth of the baby. A carbohydrate-rich pre-exercise meal should be consumed and fluids should be consumed before, during, and after exercise.
Exercise during pregnancy has many benefits. Even women who were previously inactive can safely engage in an exercise program once cleared by their physician. Following these recommended guidelines will help maintain health & fitness while minimizing exercise risks associated with pregnancy.