Some research shows that standing for a long time or lifting heavy objects is associated with pregnancy complications (such as preterm birth), but exercise is more of a protective factor for women during pregnancy. If you’re in good health with no pregnancy complications, the American Congress of Obstetrics and Gynecologists (ACOG) approves a “regular, moderate intensity” exercise program for all fitness levels, even for previously inactive women.
You can continue activity as long as your pregnancy stays healthy and you feel good doing it, but it’s important to regularly discuss the type and intensity of your workouts with your health care provider. Be willing to make adjustments in response to changes in how you feel over time.
Despite the misperception that exercise during pregnancy is risky for women and their babies, studies consistently show that those who work out when they’re expecting tend to have better health outcomes during pregnancy and delivery.
So are there any cautions besides not pushing yourself too far?
Anecdotal evidence suggests that women already at risk for preterm labor might trigger labor with exercise, but those moms didn’t experience the healthy, typical pregnancy that we’re primarily focused on here. Exercise does not increase your risk for preterm labor, and additional research finds that women who are considered “heavy” exercisers actually show lower rates of preterm birth than do women who exercise less often or with lower intensity. After 37 weeks, active women deliver 6 days earlier, on average, but these deliveries are not considered preterm.
More intense exercise is associated with an increase in blood glucose in pregnant women, but there isn’t a known impact on insulin level. It’s thought that the glucose is produced in response to the need for it as a result of intense exercise, so there isn’t likely to be a surplus that would cause a risk to you.
Exercising during pregnancy does seem to make a difference, with the best outcomes reported for women who maintain a consistent workout practice from early pregnancy through the third trimester, even if they adjust the intensity and type of exercise as they near delivery.
For example, overall discomfort in late pregnancy appears to be lower in women who exercise more during the first trimester, and researchers have found that women with a history of vigorous workouts who continue to be highly active in pregnancy have lower resting heart rates and a better maximal oxygen consumption (VO2max) throughout pregnancy than do moderate and nonexercisers.
There’s a slight increase in VO2max postpartum even among recreational athletes if they maintain just a moderate level of exercise throughout pregnancy. However, while you can maintain (or even improve) your VO2max, your anaerobic working capacity may be reduced in late pregnancy even if you’ve stayed active.
Still, the takeaway message is that maintaining a consistent, moderate fitness program throughout pregnancy is good for you, your athletic body, and your baby’s healthy development.
Fit & Healthy Pregnancy is a friendly, comprehensive guide to exercising during pregnancy from athlete-moms Kristina Pinto and Rachel Kramer, MD.
Find Fit and Healthy Pregnancy in your local bookstore or online and learn safe ways to exercise for two!
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Please consult your doctor before embarking on an exercise program during pregnancy.