Is It Safe To Exercise During Pregnancy?

"Many active women are surprised at how pregnancy affects their workouts," says Renee M. Jeffreys, M.Sc., a prenatal-fitness consultant in Milford, Conn., and co-author of Fit to Deliver (Hartley & Marks). "But remember that these are normal, short-term changes." Of course, exercise during pregnancy depends largely on what your fitness level is, which trimester you're in, and how you're feeling, Jeffreys says. But this much is certain: The gym is a great place to be when pregnant. If one cardio machine or strength exercise isn't comfortable, there's always another one to try. 

Getting yourself to the gym may take an extra dose of motivation, but the payoff is huge. Consistent exercise during pregnancy can minimize aches and constipation, help you sleep better, and lower your risk of gestational diabetes and depression. You may even end up having a shorter, less complicated labor. Developing good workout habits during pregnancy will help you get your body back faster after delivery too.

What’s more, exercise keeps your endorphins (your body's natural "happy" chemicals) flowing, says prenatal trainer Erinn Mikeska, owner of Delivering Fitness, in Dallas. That's a crucial benefit, especially since we now know that there are more mood disturbances during pregnancy than postpartum, due to the massive influx of extra estrogen and progesterone (hormones linked closely to mood), says Melanie Poudevigne, PhD, health and fitness management program coordinator at Clayton State University, in Morrow, Georgia.

Will Exercise Harm My Baby?

Many newly pregnant exercisers worry about miscarriage, thanks to age-old myths that say a bout of strenuous exercise can harm the baby. But "there is no real evidence that exercise is linked to miscarriage," says Bruce K. Young, MD, coauthor of Miscarriage, Medicine & Miracles (Bantam) and professor of obstetrics and gynecology at New York University School of Medicine. However, early in pregnancy, elevating your core body temperature may be damaging to the fetus, so stay hydrated, don't exercise outdoors in the heat of the day, and avoid huffing and puffing so hard that you can't talk.

Heavy exercise isn't going to hurt your baby, but it will tire you more quickly than it did pre-pregnancy. Blood volume doubles during pregnancy, and a woman's heart needs to work harder to push all that blood around—including circulating it through the placenta, an extra organ. "That means the stress on your heart will be 50 percent greater for the same exercise that you were doing before pregnancy," Dr. Young says.

How Will I Feel?

Pregnant women often notice that they feel out of breath more quickly than they used to. You may assume this is a sign that you're out of shape. In fact, during pregnancy, you're breathing 20 to 25 percent more air because you need to get rid of the carbon dioxide levels in your own blood – and in your baby's. (Babies in utero aren't breathing on their own, but they're still producing carbon dioxide, which transfers to the mother's blood.) "So breathing more doesn't mean you're any less fit," explains Dennis Jensen, PhD, lead researcher on a Queen's University study of exercise and respiratory discomfort during pregnancy. It simply means that your body is adapting exactly as it should.

You may also feel less balanced when exercising while pregnant. "Looser joints and a changing center of gravity as the pregnancy progresses alters a woman's sense of balance, making her more susceptible to injuries such as sprained ankles and knees," says Shannon Clark, MD, associate professor in the department of obstetrics and gynecology at the University of Texas Medical Branch (UTMB) in Galveston. For any high intensity workouts, find an instructor knowledgeable on how to alter workouts to accommodate pregnant women.

Pregnancy isn't the time to push yourself to the max, but it's also okay—and good for you—to get your heart rate up with cardiovascular exercise. Although a target heart rate of 140 is a number that's often cited, there's no precise number to shoot for.

Best Exercises During Pregnancy

If you have access to prenatal exercise classes, sign up. Not only are the workouts modified for pregnancy, but you also get to bond with your fellow moms-to-be over charming symptoms such as heartburn, swollen feet, and hemorrhoids. You might even get labor tips.

If your favorite classes don't come in the prenatal variety, it's fine to keep going, as long as you pay attention to how your body feels, limit your intensity, and stay within the normal range of motion. Just make sure the instructor knows you're pregnant and is knowledgeable about modifications you can make, Jeffreys advises. Also, if your instructor hasn't worked with pregnant women, find one who has.