Pregnancy Exercise Myths - Debunked

Only 40% of pregnant women un the US exercise, and only 15% of pregnant women in the US meet the bare minimum physical activity guidelines set out by the CDC.

Read that again:

ONLY 15% OF PREGNANT WOMEN ARE MEETING THE BARE MINIMUM PHYSICAL ACTIVITY GUIDELINES IN THE US.

What's worse, an international study of over 28,00 women found that the physical activities that most pregnant women participate in are qualified as "domestic activity" (cleaning, etc). and not as exercise at all. 

The data is somewhat unsurprising... only 40% of the US female population on the whole meets the minimum recommendations for weekly physical activity. 

But on the opposite side of the same coin, the data is VERY surprising. Health, wellness, and fitness trends are booming in the US, and pregnant women receive some of the most intense and involved healthcare of all, with weekly to monthly visits, regular imaging, and routine lab testing as the standard of care. (It's the postpartum women that aren’t given enough information about their recovery, but that’s for another time…)

So why? Why are pregnant women not exercising? 

There's an argument for time... you have to assume that many women are pregnant with their second, third, fourth, etc baby, which limits availability for exercise. These days, many moms work... so our workout time in general is limited to before and after work. And then there's pregnancy symptoms... nobody wants to exercise when they're nauseous, puking, and falling asleep in the middle of the day - or when they feel so big they start referring to themselves as a "beached whale."

But then there's another argument... an argument that looks at the many, many myths about pregnancy and exercise that have been passed down through generations and simply aren't being addressed by the medical community... or are perpetuated because the rules are so vastly generalized that the advice given to highly physically fit population is just the same for the least physically fit of all. 

So let's look at - and debunk - those myths about pregnancy and exercise! 

Myth #1: Pregnant women shouldn't exercise.

Other related myths include: exercise during pregnancy will cause pre-term labor or negatively affect the weight of the baby. 

If you have any interest in exercise at all, I'm sure the thought has crossed your mind - can I exercise while I'm pregnant? YES. I'm here to tell you the answer is YES, and if anyone tells you otherwise, you should run screaming in the other direction. 

A large meta-analysis study has the facts - aerobic exercise and moderate-intensity strength training exercise performed 3-4 days per week throughout a pregnancy were NOT associated with an increased risk of preterm births or low birth weight infants in normal weight women with singleton, uncomplicated pregnancies. 

SO, in an uncomplicated, healthy, single-baby pregnancy, it is perfectly safe to start or continue an exercise program. In fact, exercise has been shown to have the following benefits in pregnant women (and most of these actually apply in all populations):

You should NOT start or continue an exercise program confirming with your medical provider or if you suffer from a heart or lung disease, cerclage (cervix sewn shut), pregnancy with multiples, placenta previa after 26 weeks, preterm labor during this specific pregnancy, after your water has broken, pre-eclampsia, severe anemia, or vaginal bleeding. 

Drink more water than you used to! Wear a sports bra that fits well. Avoid exercises that will increase your core temperature, like hot yoga or pilates, or exercising in extreme heat. Know your limits - you’re going to fatigue earlier, it’s just a fact. If you don't already live there, try to stay below 6000 feet. Also avoid contact sports (football, soccer, MMI), sports with a danger factor (skydiving, scuba), or sports with a fall risk (snow sports, waterskiing, off-roading, horseback riding, gymnastics).

Myth #2: There is an increased risk of miscarriage in the first trimester when you exercise while pregnant. 

Absolutely, positively not true. Safely exercising while you're pregnant, at any point in your pregnancy, will not increase your risk of miscarriage. In fact, most miscarriages - while devastating emotionally - are completely out of your control and due to chromosomal abnormalities. In my research I also came across a really interesting article that discussed mothers who miscarried and were not exercising. The short version? A sedentary lifestyle may actually amplify the emotional impact of a miscarriage as the emotionally protective benefits of exercise will not be present to address the deep sadness that can follow a pregnancy loss. But the big takeaway - safe exercise will not cause you to lose your baby.

Myth #3: You shouldn't start a new exercise program while pregnant.

Not necessarily. It's safe to say you shouldn't start an Olympic lifting program while you're pregnant. But expanding your movement to include strength training - or walking, elliptical, yoga (not hot), swimming, jogging, spinning, or even some HIIT workouts - can be extremely beneficial while pregnant. This season may actually even be the ideal time to start a new exercise habit, with your health and baby's health as a motivational factor where you’ll feel an immediate impact. If you are starting a new exercise program while pregnant, make sure to speak to your OB to confirm there are no nuances to your specific pregnancy that will limit your access to specific activities, and work with a prenatal exercise specialist (like me!) so that you can progress slowly and safely. 

Myth #4: During prenatal exercise, you should keep your heart rate under 130, or 140, or 150 bpm. 

First of all, the fact that this "rule" includes three completely different heart rate numbers depending on the source should be proof enough that it's not trustworthy advice. No steadfast scientific rule has such a high level of variation. This guideline was actually introduced in 1985 (38 years ago, people!). In 2020, the ACOG updated their recommendations to "fairly light" exercise at 60-80% of age-predicated max heart rate, "usually not exceeding 140 bpm"). 

But here's the deal... I'm 34. 80% of my age-predicted heart rate max is 149 bpm; 60% is 112 bpm. If you're a pregnant woman in her early 20s, say 24, 80% of your HRmax is 157. What I'm saying is that this number fluctuates hugely depending on your age at pregnancy, and the difference between 60% and 80% is also huge. 60% of HRmax also keeps us closer to a fat burn zone, while 80% takes us closer to a cardio fitness state. Not to mention, it's going to take harder, more intense exercise to reach a higher heart rate in a more physically fit person than it is in a sedentary person - so the definition of what comprises moderate intensity exercise is highly individualized. Your heart rate can even fluctuate week by week during pregnancy due to changing blood volumes.

Heart rate is a horrible tool to measure exercise intensity because there are so many variables.

It’s a good guideline, and you should know the range to stay within, but it’s not the best guideline to determine how you exercise while you’re pregnant. Instead, you should use other markers to measure your exertion. Make sure you're not so out of breath that you're able to speak while you're exercising, that you're able to exercise with good form, and that you're not feeling dizzy, lightheaded, or nauseous because of exercise. It goes without saying that you should also stop exercising if you start bleeding vaginally. Listen to your body. (And aim for 11-13 on the Borg Scale, linked here).

To calculate your age-predicted max heart rate, subtract your age from 220. Then find 60% or 80% with typical arithmetic... 80% of 220-34 = 149 bpm

Myth #5: Core work, abdominal exercises, exercises on your back, and exercises that include twisting will be harmful to baby during pregnancy, or increase your risk of ab separation/diastasis. 

Wrong, again!

Let's start with core work and abdominal exercises. As for squishing the baby... there are layers, and layers, and layers and LAYERS of protective tissues and fluids that will keep you from squishing your baby during core work. But if you're worried about being uncomfortable because you're compressing your belly, there are PLENTY of exercises you can do to work your core instead - like balance and anti-rotation exercises, core bracing, functional exercises, or exercises with a dynamic focus. These types of exercises will also help to prevent or minimize the effects of diastasis recti by continuing to provide the abdominal strength you need to create a stable trunk.

Exercises on your back, on the other hand, aren't so cut and dry. It's true - when you lay on your back in the second half of pregnancy, the weight of the baby can compress your blood vessels and limit blood flow back to your heart. However, so long as you're not dizzy, short of breath, or nauseous, you can spend up to 30 seconds on your back later on in pregnancy without harming yourself or the baby. If it's not comfortable, don't do it - but without symptoms, you can lay on your back safely during exercises for very short bursts of time. 

Finally - twisting. Just like with core work, there are layers of protective tissues had fluids that will keep you from compressing your uterus. Our spine and our hips actually NEED to twist, to rotate, function properly. 

Your thoracic spine - the 12 levels between your shoulders and your waist - is meant to be rotationally mobile. This part of your spine is where you should see the most motion, and when you lose that mobility, you need to make it up elsewhere - namely, your neck and low back. And when your neck and low back start to become more mobile, they also get less stable - which means your muscles have to work harder to maintain trunk stability, which means suddenly you're sore and in pain. 

Your legs, on the other hand, also need to rotate on your pelvis - creating hip mobility that will prevent pain across your whole body. Lack of internal rotation (turning your foot inwards while keeping your pelvis stable) or external rotation (turning your foot outwards) can lead to back pain, knee pain, and even foot pain. When you don't rotate your hip on your pelvis, you also create compensatory tightness in the pelvic floor that can cause tailbone pain and even constipation. (Check out my favorite hip mobility drill here!)

With twisting, what you do want to avoid is deep, aggressive rotations -- don't create discomfort, don't go into a deep yoga twist, and don’t push beyond what's even a little uncomfortable. But to maintain mobility - you need to twist! 

Myth #6: The only value of exercise during pregnancy is to lose weight after baby.

Only partially true. There is major value in exercise during pregnancy when it comes to postpartum weight loss. But that's not the ONLY benefit. And if you scroll up, you'll see a nice long list of the benefits of exercise during pregnancy - exercise creates improvements in every system and function of our body, especially our metabolic function and our cardiovascular system. 

But this is also a great place to talk about the prevention component of exercise. Body positivity movement or not - obesity is an epidemic in our country, and the health risks of a significantly high BMI are severe. In pregnancy, obesity is linked to higher rates of spontaneous abortion (miscarriage), neural tube defects in baby like cleft palate, spina bifida, and hydrocephalus, and even greater risk of stillbirth. The health of your baby is directly linked to your metabolic health.

So what do you do?

The moral of the story here is that you need to exercise while you're pregnant. You need to meet the minimum CDC requirements for exercise, which are 150 minutes of weekly physical activity of at least moderate intensity. You need to be aware of the precautions, be aware of the red flags, and listen to your body. Most importantly, you need to take care of yourself because, well, it's important to take care of yourself! 

Remember, every pregnancy is unique, and staying active within your comfort level can have countless benefits for both you and your baby. So, let go of those outdated myths, get yourself a brand new comfy sports bra, and lace up those sneakers – it's time to embrace the power of safe and enjoyable exercise during pregnancy.