3 Ways Pregnancy Changes Your Heart Rate

It turns out that pregnancy affects more than one of your body systems!!

Forgive my French, but no Sh!t, Sherlock! You are growing another human, you superhero, you!! Of course we will have changes to MULTIPLE body systems as pregnancy progresses!!

But do you know HOW being pregnant changes your cardiovascular system (heart and blood supply) and WHAT this means for your daily workout, and life activities? 

It’s me, Dr. Kelly Sadauckas, Double Board Certified Pelvic PT, here to demystify all things related to your pelvis and pelvic floor for you, and reduce your anxiety and fears around pregnancy!  I’m glad you’re here! Read on to learn more about three important ways that being pregnant changes how your heart responds to life, and exercise, my friend!

How pregnancy affects our heart’s response to life and exercise.

 1. Pregnancy increases our overall blood supply

You are literally growing another human, inside of your body. To do this, your body needs more blood, all around.  Hytten, as long ago as 1985, knew that the pregnant women's blood volume increased 30-50% during pregnancy!!  This extra blood is used to support the uterus, and developing baby with necessary nutrients, and to clear the waste products.

And to develop this extra blood requires the right nutrients!  I have amazing YouTube and Instagram collaborations with Lindsay Jones, and Integrative Health Nutritionist, that are absolutely worth a watch, to learn more about the nutritional requirements of pregnancy.  And if you want to work with someone in person, I can personally recommend Lindsay as effective, understanding, and able to work with clients worldwide, via online visits. ...but where were we?  Ah, yes, the changing blood volume...

This change in blood volume, and how our brain, kidneys and heart, manage this increase in blood, doesn’t happen overnight. Since it takes a while for the actual increase to happen,  'how' the body reacts, and 'how' we need to adjust our workouts (& daily life), varies depending on where we are in our pregnancy.  And YOU need to know this, to know what to expect, and how to adjust workouts and life, to optimize your comfort and ability to participate in activities that you want to do, as pregnancy progresses. 

 2. Early in Pregnancy, Our Body Isn't Used to the New Volume Yet, So Your Heart Rate Will Be Unusually High in Response to "Easy" Tasks

Early in pregnancy, we have all this new blood volume, but our body is still using its 'old' heart rate and blood pressure to manage this new volume...and it's just the right mix.

Add into this, the fact that your blood vessels are relatively alll "loosey-goosey" (to use a technical term), so they aren't necessarily "pushing the extra blood" out of the limbs back to the heart and brain.

So if this extra blood is stuck in our legs and hands...it's not in our brains. And your amazing body notices this, and reacts by increasing your heart rate, to get the appropriate amount of blood to your brain.  

Isn't that great??  Our bodies are SO COOL!!

So early in pregnancy the brain will increase your heart rate, in order to get enough blood (which carries oxygen and nutrients) to vital organs, like your brain, kidneys, etc.

This explains why, at 10 weeks, you might not even be showing yet, and your heart is racing from walking up and down the stairs once. And why your heart rate might be a bit high, even at rest.  

Practical Implications for Monitoring Exertion, or Heart Rate, Early in Pregnancy

So early in pregnancy, while the body is still figuring out what to do with all this blood, it’s important to use the “Rating of Perceived Exertion” or “Relative Perceived Exertion” to measure how hard you are working out, and NOT your heart rate. 

My next blog post is ALL ABOUT this, but here is the cliff notes on the RPE scale: Rating of Perceived Exertion is a scale from 0-10 that helps you gauge "how hard" you are exercising/working in life.  0 = sitting on your arse, 10 = Olympic effort (or running from a tiger).  Your goal should be to do things that are 5-6/10 on this scale, as your "max" for your workout...and this might mean that something that "used to be a warm-up and easy for you" might now be your workout.  And that's 100% okay.  Listen to your body, friend. 

Implication for Exercise in Early Pregnancy: Work out “medium hard to hard” for at least 20 minutes 3x/wk for amazing health benefits to you and baby.  This is a 5-6 out of 10 on the RPE scale.  Don’t worry if you “think you should be able to do more.” Do what you can, and respect that you are growing another human inside of you, and that this level of activity is PERFECT for giving positive benefits to you and baby!!

Sidenote: this “loosey-goosey-ness” of the blood vessels that leads to the blood staying in the arms and legs and not the brain…it could lead to swelling of the legs and arms (and hands and feet)...while that is “common” in pregnancy, it can also sometimes be a sign of less-than-ideal situations.  Wearing compression stockings in exercise can help, but you may need to talk to your doctor about checking your blood pressure to ensure you are safe and healthy as baby grows.

Talk with your health care provider about checking your blood pressure, and if blood pressure is normal, consider compression stockings. These are super fun, and these tights were vital to me on long work days or airplane rides in each of my pregnancies. And all of the Physical Therapy staff at Pelvic Floored are trained in measuring for Lymphedivas (& Lymphedudes) Compression Garments, so be sure to make an appointment if you want some of those fun ones, today!!

 3. Later in Pregnancy, Our Amazing Body Adapts to this New Blood Volume

Later in pregnancy, your body has now adjusted to the 'flexy' vessels, making them stiffer and better to handle the increased amount of blood in your system. This means that your heart is filling more efficiently, pumping more efficiently, and your blood vessels are delivering the blood like rock stars.

Your heart is now effectively in "Beast Mode", and therefore not having to beat as fast, and moving A LOT of blood in a really good way. So now your heart rate is lower…even with hard things. 

Implication for Exercise in Later Pregnancy

So practically, this means that later in pregnancy, you might feel like you're really working hard, but if you are using heart rate to monitor exertion in pregnancy, your heart rate might never reach the “target rate” you are shooting for, even though you feel you are working moderately hard to hard.

Therefore, later in pregnancy, we still want to use the RPE scale to monitor exertion (target workout medium hard to hard), and don’t worry if you think your heart is beating slower than it ‘should’ be.  Take that as a sign of you being a superhuman, you :) 

To summarize heart rate changes in pregnancy:

• Early in pregnancy, heart rate is higher than usual even with "easy" tasks. 
• Later in pregnancy, it is lower than usual, even with "hard" tasks. 
• Using RPE scale of 5-6/10 (“moderately hard to hard”) is the Goldilocks Zone for Exercise in Pregnancy, and will keep you in "the right zone" for you and baby. 
• Excessive swelling of feet and hands can be a sign of heart and circulatory system problems in pregnancy.  Meet with a primary medical provider, and have your blood pressure checked if you are experiencing lots of swelling.  Elected blood pressure in pregnancy must be controlled, (usually with. medication, occasionally also with bedrest or emergency C-section), or it can be a life-threatening for mom and baby. 
• If you, or a loved one has elevated blood pressure in pregnancy that is not being monitored, or actively managed, by a medical team, get a new medical team. 

Wow.

So that's how your heart rate changes during pregnancy as your rad body grows this human, and how you can understand why using rating of perceived exertion (RPE scales)  is the best way to pick the best intensity for exercise in your pregnancy.

I sure hope this post is helpful to you!!  Please know that Pelvic Floor PTs can be a  huge asset to your birth preparation. Even just ONE visit of PT to connect to your body and your needs, can lead to HUGE gains in understanding the labor and delivery process, as well as what you can do to reduce the risks of perineal tears (beyond just knowing about positions) 😃. Here’s how to find a Pelvic PT near you, or here’s my scheduling site if you’d like to work with me, or another WORLD-CLASS member of the Pelvic Floored Staff.  We have in-person visits available in Idaho, and online visits available worldwide.

For those seeking alternative avenues, perhaps you’re not ready to see a Pelvic PT in person, consider a high-quality online course from a trusted professional. Pelvic Floored offers world-class streamable pelvic wellness programs, that you can work through at your own speed, in the comfort and privacy of your own home, for a fraction of the cost of one:one Pelvic PT.  Push Prep is my delivery-focused streamable course, and it includes in-depth knowledge in labor positions, as well as instruction in perineal stretching, counter-pressure techniques for birth partner, and more!  The Pregnancy Course  , originally "Your RAD Pregnancy" is actually a bundle of 3 courses: Bump Lab, Weight Lifting in Pregnancy and Pregolicious.  Bump Lab is a pregnancy prep class that actually teaches you functional things about your amazing changing body (including nutritional tips).  Weight Lifting in Pregnancy provides you with guidance and full workouts for each trimester, as well as a handy list of substitution options if a class, or video, is doing something you’re not comfortable with.  And Pregolicous provides exercises and tips and tricks for managing many "common but not normal" pains in pregnancy, including back pain, leaks, shoulder pain and more.  And if YOU want it all The Pregnancy & Delivery Bundle includes The Pregnancy Course AND Push Prep, and saves you a few bucks while you're at it.  

K--I'm glad we can explain to you why  your heart rate is changing as your body is changing.  Check back here soon for more tantalizing info on the "Rating of Perceived Exertion" Scale in pregnancy.   I'm really glad you're here, and honestly blessed to be a part of your education and journey.  

xoxo, Dr. Kelly 😊

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References

Hytten F. Blood volume changes in normal pregnancy. Clin Haematol. 1985 Oct;14(3):601-12. PMID: 4075604. Link to study here.