Exercise in Pregnancy
Kelsey McLaughlin, PhD
‘To our knowledge, there is no intervention that we as providers can recommend to pregnant women as impressive in its significant impact on so many maternal and perinatal outcomes [as exercise].'
- Berghella, American Journal of Obstetrics and Gynecology 2017
Benefits of exercise in the non-pregnant population
When you exercise, you stimulate a response across your whole body, including your lungs, heart, blood vessels, hormones and skeletal muscle. Exercise has a wide range of benefits that improve both physical health (cholesterol levels, blood pressure, cardiac function, diabetes, osteoporosis) and psychological health (depression, anxiety).
A recent study published in an American Heart Association journal evaluated how lifestyle factors can contribute to overall life expectancy in American adults. Exercising even 1 hour a week was found to be associated with longer life expectancy. Adoption of exercise and additional positive lifestyle factors, such as modifying smoking habits, diet quality, alcohol intake and body weight, could prolong life expectancy by 14 years in women.
Exercise before pregnancy
A study from the American Diabetes Association found that higher levels of pre-pregnancy exercise were associated with a lower risk of gestational diabetes during pregnancy. Studies have also linked pre-pregnancy exercise to lower weight gain during pregnancy. Similar to the concept of a prenatal vitamin, pre-pregnancy exercise and physical activity may help prepare the mother’s body for the physical demands of pregnancy.
Benefits of exercise during pregnancy
Exercise has many beneficial effects in pregnant women. According to the American College of Obstetricians and Gynecologists, exercise during pregnancy promotes healthy gestational weight gain, improves overall cardiovascular health and fitness, reduces back and pelvic pain, and improves constipation. Importantly, women who participate in moderate exercise during pregnancy report an overall improved perception of health, compared to women who didn't exercise during pregnancy.
Recent research has shown that exercise during pregnancy may be an effective strategy to improve pregnancy outcomes. A clinical trial found that obese pregnant women who participated in an exercise program (3 cycling sessions per week, 30 minutes each session) were less likely to develop gestational diabetes (22% in exercise program vs 41% not in exercise program).
Aerobic exercise during pregnancy is associated with lower incidence of hypertension in pregnancy, when compared to pregnant women who did not exercise (6% vs 9%). A recent meta-analysis reported that exercise in pregnancy reduces the risk of developing hypertension in pregnancy by over 75%.
Numerous studies have also determined that exercise in pregnancy also lowers rates of Cesarean sections (read here).
Data from clinical trials shows that exercise does not impact rates of preterm birth, length of pregnancy or the baby's birth weight in pregnant women of average weight. However, in overweight or obese pregnant women, exercise significantly reduced the rates of preterm birth.
Although we now have convincing evidence that exercise improves pregnancy outcomes and prevents disease development, the mechanism of exactly how exercise benefits pregnant women is not known. In the non-pregnant population, we have evidence that exercise improves blood vessel function in obese and diabetic individuals (read more here, and here). Even short-term exercise programs have been found to decrease blood pressure, fasting insulin, fasting lipids and cholesterol levels in men. Together, these beneficial effects of exercise may help to protect the maternal system from disease development during pregnancy.
Exercise guidelines for pregnant women
The Society of Obstetricians and Gynaecologists of Canada recommends that pregnant women in healthy pregnancy without contraindications should be encouraged to participate in both aerobic (cardio) and strength-building exercise, without trying to reach peak fitness. The Canadian Society for Exercise Physiology has developed a guideline for heart rate target zone and other valuable information regarding activity during pregnancy. A handy rule of thumb is the ‘talk test’ - pregnant women should be able to comfortably maintain a conversation while exercising.
Similarly, the American College of Obstetricians and Gynecologists recommends that exercise is safe for healthy women during normal pregnancy and does not increase risks of miscarriage, low birth weight, or early delivery.
Despite these recommendations, a study from 2004 reported that only 15% of American pregnant women were participating in the recommended amount of leisure-time physical activity.
The Society of Obstetricians and Gynaecologists of Canada outlines certain types of exercise that should be avoided, due to the potential to cause fetal trauma through impact (e.g. hiking, horseback riding, downhill skiing).
In the pregnant and non-pregnant populations, contraindications to exercise do exist. The American College of Obstetrics and Gynecologists summarizes which pregnant women should avoid exercise and outlines situations when pregnant women should stop exercising and seek medical assistance.
Pregnant women are recommended to exercise during pregnancy, unless contraindications exist. Exercise has consistently been shown to improve mom's health and improve pregnancy outcomes. Guidelines with useful information regarding exercise in pregnancy has been developed by The Canadian Society for Exercise Physiology
Every woman and every pregnancy is unique. Pregnant women should speak to their healthcare provider to ensure maternal and fetal safety. This article is meant to provide readers with current information and opinions. All medical and treatment decisions should be discussed with your healthcare provider.