June 18, 2012 by Rebecca Dekker, PhD, RN, APRN
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Have you ever wondered if you should exercise during pregnancy? Is exercise safe during pregnancy? What are the benefits? Are there any risks?

When I was first pregnant with my daughter in 2008, I asked my doctor if it was okay to exercise during pregnancy. She told me it was okay, but I needed to keep my heart rate below 140. So at about 10 weeks pregnant, when my early pregnancy fatigue started going away, I went to the gym. I had always been very fit and healthy before pregnancy. So I was surprised when I tried the exercise bike, and within 5 minutes my heart rate was above 150. I tried the stair stepper. 150. I tried the eliptical. 150. I couldn’t find any piece of exercise equipment that I could exercise on that would keep my heart rate below 140. I ended up just walking circles around the track.

In my second trimester, I discovered prenatal yoga and prenatal water aerobics. I chose prenatal yoga and water aerobics for 3 reasons: they were relaxing, they helped prevent my pregnancy-related migraines, and I was able to do those 2 exercises without my heart rate going above 140. The effects of yoga and water aerobics on my migranes were tremendous. These 2 prenatal exercises were an important part of a migraine prevention plan that I developed with my neurologist. Although there is no research evidence looking at yoga and swimming for the prevention of pregnancy-related migraines (add this to the list of studies I want to conduct some day!), my neurologist recommended this exercise routine based on what he had seen work for pregnant patients in his clinical practice.

Interestingly, Dr. Shannon and I have both searched, and we cannot find any evidence  to support the recommendation that you have to keep your heart rate below 140 during prenatal exercise. If anybody knows of any research on the preferred heart range for exercise during pregnancy, please let me know in the comments below!

So what is the evidence for exercise in pregnancy? For this article, I decided to look mainly at meta-analyses on exercise in pregnancy. A meta-analysis is the gold standard of research evidence. In a meta-analysis researchers take a bunch of studies and combine the results to come up with an overarching conclusion.

In a Cochrane review (Kramer & McDonald, 2006), researchers combined results from 14 randomized, controlled trials that compared exercise (moderate exercise for at least 30 minutes that took place at least 2 times per week) and no exercise in 1,014 low-risk pregnant women. Unfortunately, most of the studies were not of very good quality. The researchers looked at the results of exercise on aerobic fitness and pre-term birth. However, the different researchers all defined aerobic fitness in different ways, which made it difficult for the Cochrane reviewers to combine results. Also, only some of the studies looked at pre-term birth. The results? It appears that from the limited knowledge we gained from these studies, regular aerobic exercise during pregnancy either maintains or improves physical fitness in pregnant womenExercise probably does not have any effect on pre-term birth (that’s a good thing!). We can’t tell any other risks or benefits of exercise from this Cochrane review.

In a more recent meta-analysis, researchers looked at 12 randomized, controlled trials with 1,073 low-risk pregnant women to determine whether exercise prevents excess weight gain during pregnancy (Streuling et al., 2011). The quality of the studies was mixed, with some studies having good scientific quality and others not so good. Women in the exercise groups participated in exercise routines that ranged from 20-60 minutes per session, with at least 3 sessions per week, starting during the first or second trimester and lasting until delivery. Exercises that were tested included aerobics, running, cycling, water aerobics, or muscle strengthening. The authors found that women who exercised gained less weight during pregnancy. This is an important finding, because gaining too much weight during pregnancy can increase the risk of several not-so-good outcomes: large infant size, difficulty losing pregnancy weight gain post-partum, and the risk of your child being obese when they are 3 years old. Although the effect of exercise on weight gain was significant, it was clinically small. On average, women who exercised gained 1.3 pounds (or 0.6 kg) less than women who don’t exercise. However, the authors stated that though this may be a small effect in individual women, it could have important implications if this effect was spread across an entire population of pregnant women.

Finally, I hope you read my post last week on gestational diabetes and the glucola test. Although much of our attention has been focused on detecting gestational diabetes and getting treated for it, did you know that there is an easy way to help prevent gestational diabetes all together?

In another meta-analysis, Tobias et al. (2011) combined the results from 8 studies that examined the relationship between exercise (before or during early pregnancy) and the risk of getting gestational diabetes in almost 35,000 women. The review included studies that were randomized, controlled trials as well as observational studies.  The results? Regular physical activity before you get pregnant reduces your risk for gestational diabetes by 55%! And… regular physical activity during early pregnancy decreases your risk for gestational diabetes by 24%. What types of regular physical activity were found to be associated with a decreased risk of gestational diabetes? Brisk walking, stair climbing (>10 flights/day),  and other vigorous physical activities. (This does not mean that other types of physical activity are not beneficial—just that they were not specifically examined by the researchers). (Tobias, Zhang et al. 2011)

So there you have it– the evidence for exercise during pregnancy. Exercise throughout pregnancy maintains or improves physical fitness and helps reduce your risk of excess weight gain during pregnancy. Exercise during early pregnancy reduces your risk of gestational diabetes. And most compelling of all– exercising before you get pregnant cuts your risk of gestational diabetes in half! So here is my challenge for you– pregnant or not, do not take the elevator anymore unless you have a medical reason for taking the elevator. Every time you see a stair case, walk those steps!! Every flight of stairs counts!

Disclaimer: In terms of the risks of exercise, I did not see any in the literature I reviewed. However, it’s always a good idea to talk with your health care provider before starting an exercise routine. The American Congress of Obstetricians and Gynecologists (ACOG) has a good article with a list of people who should NOT be exercising, as well as warning signs that mean you should stop exercising (a lot of it is common sense– for example, if you start bleeding while you are exercising, stop!). You can read the ACOG exercise guidelines for free here.

References:

  1. Kramer, M. S. and S. W. McDonald (2006). “Aerobic exercise for women during pregnancy.” Cochrane Database Syst Rev(3): CD000180.
  2. Streuling, I., A. Beyerlein, et al. (2011). “Physical activity and gestational weight gain: a meta-analysis of intervention trials.” BJOG 118(3): 278-284.
  3. Tobias, D. K., C. Zhang, et al. (2011). “Physical activity before and during pregnancy and risk of gestational diabetes mellitus: a meta-analysis.” Diabetes Care 34(1): 223-229.
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