Disclosure: I’m a bit of a data nerd.
Not in the sense that I like to design studies and collect data. Just in the sense that I like to look at charts and graphs and timelines and other visuals.
Call it “data-nerd-light.”
I began wearing a FitBit Charge HR last February, shortly after I started running as a regular form of exercise.
At first, it was useful for keeping track of my exercise. Having information about my sleep patterns and steps was just fun information to use to challenge myself.
Then, in early May 2016, I got pregnant.
Over the course of my pregnancy, I regularly wore my FitBit and amassed loads of interesting data about how my body changed and responded differently to exercise over the course of my pregnancy.
The FitBit Charge HR will monitor your heart rate and calories burned, as well as your number of steps, floors climbed, and miles traveled. Then, it spits out all of this data into usable and easy-to-read charts. (UPDATE: My Charge HR started separating around the display and I had to replace it after 16 months of use. I recently upgraded to the Charge HR 2. It’s just $20 more and much more durable. The bands are replaceable too, so the same problem can’t happen on this model.)
I started this pregnancy at 147 pounds (at 5′ 7.5″) and my ending weight was 192 pounds, which is a 45-pound weight gain. My pre-pregnancy condition was quite good. I was running about two miles in the morning every day and lifting weights once or twice per week. I was maintaining my weight. I had good energy. I could climb several flights of stairs without getting winded.
So what does pregnancy do to a healthy body? Let’s take a look.
Resting Heart Rate
My pre-pregnancy resting heart rate was about 56 beats per minute, a sign of a fairly athletic lifestyle. You can see my heart rate climb steeply in the second trimester when I have my first major growth spurt, and then again in the last trimester during the last month of growth. Both time periods correspond to an increase in blood volume in my body.
Fun fact: at the end of pregnancy, a woman’s blood volume increases 40-50% throughout pregnancy.
I put on most of my weight during the second and third trimester growth spurts, and just a few pounds gained in the first trimester. This is a healthy weight gain curve, although, I assure you, it didn’t feel healthy at the time. I remember that I kept thinking, No! Four pounds in a week! This baby is going to be twelve pounds by the end of this!
Daily Calories Burned: Pre-Pregnancy
On the left is a typical day of exercise on a pre-pregnancy day, which includes a two-mile run in the morning and regular movement at work.
On the right is a day that I’m proud of: the day that I ran six miles around the National Mall in Washington D.C. Included in this number are the other calories that I burned throughout the day, just by existing. See the number of calories burned? Keep that in mind as I show you how many calories during the late third trimester.
Daily Calories Burned: First Trimester
In my first trimester, I continued to run whenever I felt well enough. (Weeks 7-11 were Nausea City, so I limited my exercise to walks during this time.) But I took it easy. I didn’t exercise in the peak heart rate zone if I could help it. I monitored my run pretty closely so I stayed in the lower heart rate zones.
Daily Calories Burned: Second Trimester
I continued to run in the second trimester. In the early second trimester, I incorporated more indoor aerobic exercise because it was so damn hot outside in late July to August. In this screenshot, you see the end of October, when I was 24 weeks pregnant, right at the end of my second trimester growth spurt.
The important difference is my resting heart rate, which has jumped to 70 beats per minute. Because of that elevated resting heart rate at this point, I was more likely to reach a fat-burning heart rate for daily activities, beyond the time when I was intentionally exercising.
Daily Calories Burned: Early Third Trimester
I continued to incorporate running in my exercise all the way to 32 weeks of pregnancy, but over time, I slowly decreased my running in favor of walking. By 33 weeks of pregnancy, I was done running. This screenshot is from Week 30. It’s not terribly different from my second trimester stats. Notice that my resting heart rate continues to rise.
Daily Calories Burned: Mid-Third Trimester
This is when pregnancy becomes an outright test of endurance. This screenshot is from Week 36 (which, for my 41.5-week pregnancy, was mid-third trimester). On this day, I walked for 30 minutes. And I existed. End of story.
I mean, it’s the day after Christmas, for goodness sake. What could I possibly have done? I’m sure I was doing things like eating my fifth sugar cookie and picking up bits of wrapping paper and rogue pine needles. Along with a rousing game of “Ketchup or Mustard?” with our three-year-old. (What? You’ve never heard of that game? You just ask the person if they want ketchup or mustard over and over and over again. That’s it. Fun, huh?)
So that’s why pregnant women say, “God, I’m so tired” at the end of the day. Not only are they carrying around a lot of extra weight, but their resting heart rates are elevated, causing them to be burning loads of calories for hours.
But wait. It gets harder.
Daily Calories Burned: Late-Third Trimester
Okay. So here I was at five days past my due date. At this point, I was desperate to get this kid out of me. So I decided to go for two thirty-minute walks, which you can clearly see on the graph. My pace was much, much slower than normal because my hips were so gelatinous and my gait was off. But pace isn’t important. It’s getting the heart rate up there that counts.
With just two thirty-minute walks and existing for 24 hours, I burned as many calories as I did when I ran six miles and existed for 24 hours. Courtesy of an elevated resting heart rate and additional body weight.
In addition, my body’s center of gravity was off, it was difficult to move, and I had an assortment of new aches and pains to deal with just to get through the day (and night).
What were your calories burned on the day you gave birth?
So glad you asked.
Now, I know what you’re thinking. That peak heart rate must have happened during my pushing phase.
That was when I started hemorrhaging after the birth. Obviously, this wasn’t part of the plan and it isn’t a typical part of the birthing process for most women (thank God). Only about 4% of women will experience a postpartum hemorrhage. (The most likely cause of my PPH was an “overdistended uterus” due to my baby being over 8.8 pounds.)
As a result, my heart rate soared in the peak heart rate zone for close to an hour. As blood poured out of me, my heart pumped loads of fresh blood to the affected tissues and organs. All of this put my body into metabolic overload and it was the main reason I ate like a crazy person for the first five days post-birth.
Most of my labor raised my heart rate into a low fat-burning zone rate, so it was still important that I ate and drank during labor. This is what I will never understand about typical hospital policies regarding labor. Is it really worth it to deny women the right to eat during labor simply because of the minuscule possibility that 1) she’ll have a C-section and 2) during that C-section she aspirates?
Labor burns a lot of calories. And if you’re restricted to clear fluids, you’re pretty much relying on the sugar in Sierra Mist to pull you through. I think that if you have the urge to eat, you should be allowed to eat. The risk of eating harming a woman in labor is just far too small.
I mean, really… When you are awake for days and laboring for hours and hours, you burn a lot of calories.
So there you have it. An inside look at one slice of what a woman goes through when she carries a child and gives birth. It is a test of strength and endurance simply to carry a child to term and give birth.
The fact that women give birth so often might make the process seem ordinary, but it is truly an extraordinary feat for both mother and child to come out on the other side, whole and alive.
UPDATE: Just wanted to thank you for stopping by this post, which has been gaining a lot of traffic lately (probably because this post shows up in Google searches that include “pregnancy” and “FitBit.” Ha!) If you’re a new reader, please check out my book, Becoming Mother, available in print ($12.99) or Kindle ($2.99) editions.