When it comes to exercise during pregnancy, two predominant schools of thought exist – exercise can harm the developing baby and cause pre-term labor, or exercise builds a stronger mom and healthier baby and makes labor easier.
Many of those who follow the first school of thought learned it as a truth passed down from grandmother to mother to daughter. Yet mounting evidence supports the second school of thought that encourages exercise throughout pregnancy.
“We’ve learned a lot through research about the benefits of exercise during pregnancy,” said Karen Salazar Valdes, M.D. , an obstetrician and gynecologist affiliated with Baptist Hospital of Miami . “What we’ve discovered over the years is that moderate exercise during pregnancy in healthy women does indeed benefit the health of the mom and her baby.”
Research About Pregnancy and Exercise
An article in the March 21, 2017 edition  of the Journal of the American Medical Association, or JAMA, cites an analysis of 2,059 women, pregnant with one baby and no known health complications, that showed that moderate exercise was not associated with pre-term labor. Moreover, the article references another study that found that previously sedentary mothers who began a moderate exercise regimen during pregnancy did not compromise their pregnancy or the health of their unborn baby.
Evidence like this, which has been growing in the last decade, prompted the American College of Obstetricians and Gynecologists (ACOG) in 2015 to issue an opinion  about exercise during pregnancy.
The U.S. Centers for Disease Control and Prevention (CDC)  recommends that pregnant women engage in at least 150 minutes of “moderate-intensity aerobic exercise” each week. Aerobic exercise involves movement of the large muscles of the body in a rhythmic way. The CDC defines “moderate intensity” as raising the heart rate enough to breathe harder, while maintaining the ability to talk, and starting to sweat.
Safe Exercises and Physical Activities During Pregnancy
Following an evaluation and conversation with a doctor, most women can engage in the following physical activities while pregnant, Dr. Salazar Valdes says:
- Stationary cycling
- Low-impact aerobics
- Prenatal yoga programs
- Prenatal Pilates programs
- Running or jogging
- Tennis and other racket sports
- Strength training with weights or resistance training
For extreme fitness programs that are becoming more popular in recent years, Dr. Salazar Valdes recommends speaking about the risks with a doctor and, if approved, taking modifications that reduce the risk of injury during workouts.
Types of Exercise to Avoid During Pregnancy
ACOG and the CDC recommend avoiding the following types of exercise while pregnant:
- Horseback riding and other exercises that carry a risk for a serious fall
- Water skiing
- Mountain cycling
- SCUBA diving
- High-altitude skiing
- Contact sports, such as hockey, boxing, soccer and basketball
- Exercising on your back after the first trimester
- Vigorous exercise in hot, humid environments
Benefits of Exercise During Pregnancy
Dr. Salazar Valdes says that for most pregnant women, the benefits of moderate exercise outweigh the risks, but recommends first discussing any exercise regimen with a doctor to ensure there are no clinical reasons not to exercise.
Top among the benefits of exercise during pregnancy, Dr. Salazar Valdes says, is weight control, which is important during and after pregnancy. “A good rule of thumb that I tell my patients is that by the 20th week of pregnancy, they should have gained no more than 12 pounds,” she said. But, she also recommends that women with a body mass index (BMI) of 30 or more should only gain 15 pounds over their entire pregnancy. Keeping weight gain in check during pregnancy also helps mothers lose the weight after their baby is born.
Moving the body during exercise helps keep the blood flowing through the mother’s body and to the baby through the placenta and umbilical cord, Dr. Salazar Valdes says. This ensures the baby receives the oxygen and nutrients it needs to grow and develop properly.
As with aerobic exercise outside of pregnancy, exercise during pregnancy helps build a stronger heart and blood vessels, Dr. Salazar Valdes says. This can help ward off high blood pressure and keep blood sugar in check to reduce the risk for gestational diabetes.
The American College of Obstetricians and Gynecologists  says exercise during pregnancy also benefits moms in the following ways:
- Reduces back pain
- Eases constipation
- May decrease the risk of preeclampsia and C-sections
- Improves overall fitness
Who Should Avoid Exercise While Pregnant?
While most pregnant women can and will benefit from exercise, women with the following conditions or pregnancy complications should speak to their doctors about the risks associated with exercise before beginning to exercise during pregnancy, according to recommendations by ACOG:
- Unevaluated cardiac arrhythmia
- Chronic bronchitis
- Poorly controlled type 1 diabetes
- Extreme morbid obesity (Body Mass Index of 40 or higher)
- Extreme underweight (Body Mass Index less than 12)
- History of extremely sedentary lifestyle
- Intrauterine growth restriction in current pregnancy
- Poorly controlled hypertension or high blood pressure
- Orthopedic limitations
- Poorly controlled seizure disorder
- Poorly controlled hyperthyroidism
- Heavy smoker
Dr. Salazar Valdes adds to this list women with cervical insufficiency and those carrying multiples – two or more babies – which puts them in a high-risk pregnancy category.
‘Listen to Your Body’
While the benefits of exercise during pregnancy have been well documented by research, Dr. Salazar Valdes advises patients to listen to their bodies and stop exercising if they experience dizziness, vaginal bleeding or fluid leaking, contractions, headaches or chest pain.
“Our bodies signal us when something is not right,” she said. “It’s important to heed that warning, especially when pregnant, to prevent any injury to the mother or the baby. The key to benefiting from exercise during pregnancy is to feel good during and after it.”