Many providers give advice to their patients regarding exercise, however some of their advice may not have any literature to support it at all. If you have read any of my blogs in the past, you know that I am always promoting fitness during pregnancy. However it can be a complicated topic, especially with the vast amounts of inaccurate information that can be found across the internet and social media channels. Here are some of my favorite myths to bust:
1. Don’t lift more than 20 lbs! Recently we have seen that more women are CHOOSING to continue with high intensity and high load strength training during pregnancy. I am excited to announce that a colleague of mine is currently in the process of publishing a piece of literature that followed 673 recreational female athletes. 85% of those athletes continued to lift heavy during pregnancy until delivery and there was NO increase in complications, including high fetal weight, low fetal weight or cesarean. This just reinforces that strength training throughout pregnancy DOES NOT lead to poor birth outcomes.
2. Don’t hold your breath! Creating valsalva during pregnancy may actually be safe! Contrary to popular belief, performing valsalva during pregnancy does not create any signs of myocardial stress to mom (hemodynamic or cardiac function). Therefore, pregnant women may use the valsalva maneuver during low to moderate resistance exercises, as long as they are not experiencing any symptoms of nausea, dizziness, lightheadedness or fainting.
3. Don’t exercise on your back! If you aren’t supposed to sleep on your back, why should you sleep on your back? Well the main concern is for Supine Hypotensive Syndrome which can be caused by the weight of the fetus and uterus causing compression of some large vessels traveling to the heart. Most women will become symptomatic (nausea, dizziness, feeling unwell) within 3-7 minutes and this happens in 10% of women. With regard to exercise, most exercises do not require you to be on your back for 3-7 minutes so there is no need to scare women when it is not necessary. The literature shows that no adverse events were reported when women exercised on their backs, but if you are experiencing symptoms prop yourself up on a wedge!
4. Don’t start an exercise program until your second trimester! Prenatal exercise is NOT associated with fetal mortality. A 2019 study showed that there is NO increase risk of miscarriage for women who are physically active during pregnancy.
5. Keep your heart rate below 140 bpm! A 2012 article stated that fetal bradycardia and a significant decline in uterine blood flow was noted in women running at over 90% VO2 max/max heart rate, which is where the recommendation to watch intensity came from. We don’t know if transient dips in heart rate adversely impact baby and it is relatively abnormal for women to even get upwards of 90% of their VO2 max comfortably during pregnancy. A better way to manage intensity during pregnancy is to use the Talk Test.
Unfortunately this field still requires SOOOO much research, but it is important to educate our community on where the literature we do have stands!