Exercise Your Way to an Easier Pregnancy

by Word of Mom Blogger on March 29, 2013
author Word  of Mom Blogger

Word of Mom Blogger

About the Author




SquintMom is a science journalist, university faculty, and the chief "squint" — a squint is a geek, a researcher, someone who "squints" at data — at She spent many years in academia (and has the student loans to show for it), and since becoming a mother in 2011, she's read a lot of parenting-related research. She knows there are many moms and dads who, like her, want to make evidence-based parenting decisions, but don't have the time to comb through piles of journal articles. She started to help these moms and dads find science-based answers to their parenting questions: She squints at the data so you don't have to!

When it comes to pregnancy health, it seems everyone has an opinion. To make matters worse, while there are some things that all the experts agree upon (Don't drink! Take folic acid!), other questions seem to prompt different answers from each book you read, doctor you consult, or old woman in the grocery store who gives unsolicited advice while rubbing your baby bump in an uninvited, overly-familiar way.

Exercise during pregnancy definitely falls into the latter category, with some sources suggesting that you can feel free to run marathons and lift weights, and others warning that it's best to work out very gently, if at all. Thankfully, though, the science of exercise during pregnancy has been studied fairly extensively, which means there's evidence-based information to be had. Even better, I've combed through the peer-reviewed journal articles and summarized the scientific findings so you don't have to wade through piles of research.

Whether you're a couch potato looking to have a healthy pregnancy or a seasoned marathoner hoping to continue running, here are the science-based guidelines for tackling pregnancy exercise in a safe way:

1. Determine the appropriate intensity by feel rather than by heart rate, shooting for "somewhat hard."

You read that right: the commonly cited guideline that you shouldn't get your heart rate over 140 beats per minute during pregnancy is passé. Research shows that health benefits are maximized when exercise heart rate is 50-85 percent of maximum heart rate — this translates to approximately 98-166 beats per minute for the typical 25-year-old — according to the American College of Sports Medicine. Healthy pregnant women are no exception.

In general, pregnant or not, less conditioned individuals do best toward the lower end of this target heart rate range, while more conditioned individuals do best toward the higher end. Some very serious athletes may enjoy tracking heart rate closely, but for the rest of us, there's no reason to invest in a heart monitor. It appears that an individual's perceived effort is an excellent predictor of exercise intensity — even during pregnancy — and accounts more accurately for differences between individuals than heart rate does (Pivarnik et al). Researchers suggest shooting for an exercise effort that feels "somewhat hard." In numeric terms, your effort should be a 12-14 on a scale of 0-20, where 0 is absolutely no effort at all — as in, eating pickles and watching The Bachelor — and 20 is the hardest effort you can imagine (think "running like a wildebeest from a hungry lion").

As an interesting aside, a study of pregnant women showed that perceived effort changes relative to heart rate as pregnancy progresses; a woman who exercises at a perceived effort of 14 earlier in pregnancy has a higher heart rate than she does when exercising at that same perceived effort later in pregnancy (McMurray et al). It appears that your pregnant body understands that it's best for both mom and baby to tone it down a bit later in pregnancy, and the same workout feels harder than it did earlier on. Science bottom line: Listen your body; it will help you find the right effort level for safe pregnancy exercise.

2. For you seasoned exercisers out there, don't fret that your workouts will harm your long as you don't go overboard. Even though the guidelines suggest sticking to a perceived effort of 12-14, there's no scientific evidence that efforts near the upper end of the aerobic zone will negatively impact the baby (for those who aren't seasoned exercisers, the "aerobic zone" is the heart rate range during which your body is working hard, but you're still getting enough oxygen to burn both fat and sugar effectively. It's generally defined as 65-85 percent of your maximum heart rate). A study of pregnant women showed no adverse effects to either mom or baby with regular workouts near 85 percent of maximum heart rate (American College of Sports Medicine).

Still, there's some suggestion that regularly working out at very high intensity — the way a competitive athlete might do — could increase mom's body temperature enough to decrease the baby's birth weight, though the effects are moderate and evidence is limited (Hale et al). Science bottom line: Women who exercised hard before pregnancy can likely continue to do so during pregnancy without trouble, but competitive athletes should talk to their obstetrician about their pregnancy fitness goals, and may require monitoring.

3. Couch potatoes take note: Pregnancy is a great time to make a lifestyle change! There are several reasons to consider beginning to exercise during pregnancy, even if you weren't active before. For one thing, a sedentary lifestyle is associated with an increased risk of excess weight gain, and while that's unhealthy at any time, it's particularly detrimental during pregnancy. Too much body fat during pregnancy is associated with increased risks to the mother that include high blood pressure (and preeclampsia), gestational diabetes, and difficult birth. For the baby, an overweight mother increases the risk of stillbirth, various birth defects, and obesity during childhood or later in life.

Women who exercise during pregnancy decrease the likelihood that they'll gain too much weight while pregnant, and for those who were carrying a bit too much weight to begin with, exercise mitigates negative effects (Weissgerber et al). Further, women who exercise during pregnancy are more likely to regain or reach a healthy weight after pregnancy. Finally, because you're more motivated to make healthy choices when there's a baby depending on you to do so, you may find that it's easier to initiate and stick with an exercise program than ever before! Science bottom line: Even if you weren't much of an exerciser before pregnancy, there's no time like the present.

4. Certain types of exercise can make your pregnancy more comfortable, and your delivery easier. Late pregnancy equals low back pain, stress, and worries about a long and difficult labor, right? Not necessarily, according to researchers. It seems that certain types of exercise can reduce pain and stress. Some studies suggest that exercising in the water takes weight off the low back, reduces lordosis (low back curvature), and helps to decrease back pain (Katz et al). Others suggest that any exercise, regardless of the type, reduces the intensity of low back pain (Garshasbi et al). The reduced pain, perhaps not surprisingly, contributes to an increased sense of wellbeing in pregnant women.

Similarly, yoga appears to reduce pregnancy-related discomfort and mental stress (Satyapriya et al), though women in their second and third trimesters should avoid positions that place them on their backs or put stress on the joints and spine. All exercise, regardless of type, appears to reduce the likelihood of a cesarean delivery, possibly by increasing the strength and endurance of the mother (Bungum et al). Science bottom line: If you're not a fan of the treadmill or weight room, consider water aerobics or yoga!

5. Most activities are safe during pregnancy, but there are a few to avoid. The guidelines of the American College of Obstetrics and Gynecology warn pregnant women not to participate in activities that could result in a fall, including downhill skiing, gymnastics, and horseback riding. They further note that pregnancy affects your balance — particularly in the last trimester, as your body weight increases and redistributes — which warrants being particularly careful when engaging in activities like running, biking, or hiking. Divers take note: Scuba is off-limits throughout pregnancy. This is because breathing pressurized air underwater increases the risk of small bubbles of nitrogen forming in the bloodstream, which can be harmful or fatal to the developing baby. Science bottom line: It's a good idea to run your exercise and activity plans by your obstetrician to make sure they're safe.

Regardless of your level of fitness coming into pregnancy, the science is clear: This isn't the time to sit on the couch! If you're used to exercise and have a healthy, low-risk pregnancy, your doctor will likely give you the go-ahead to continue your activities as usual. If you're new to the gym scene, your doctor can help you formulate a plan to get in shape safely.

That said, there are a few important considerations and specific contraindications to pregnancy exercise. Certain health conditions — including an incompetent cervix, persistent bleeding, and preeclampsia — absolutely preclude exercise while pregnant. As such, it's essential to have a thorough checkup and your OB's blessing before you tackle the gym. Further, regardless of your level of conditioning, there are some clear signs that it's time to tone the exercise down or stop entirely, including dizziness, vaginal bleeding, and preterm labor (American College of Obstetrics and Gynecology). Science bottom line: Discuss your pregnancy exercise plans and goals with your doctor. If anything unusual or concerning happens during or after a workout, call your OB.