4 Mind-Blowing Things Your Body Accomplishes During Pregnancy

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Let's just say it does some wild things to keep you and your baby healthy. Read this whenever you need a reminder that You. Are. Amazing.

Last updated: June 6, 2022
6 min read
  • Research suggests that pregnancy is the energetic equivalent to running a 40-week marathon(!).
  • Your body forms a placenta to protect your baby, and markers of your cardio fitness improve to keep you both healthy.
  • Head over to the Nike (M) page for loads of motherhood support and inspiration spanning mindset, movement, nutrition, recovery and sleep.


Read on to learn more ...

*This content is designed to inform and inspire, but it is not meant to diagnose, treat or give specific medical advice. Always check with your health care provider about how to stay healthy and safe before, during and after pregnancy.

Real talk: loving every aspect of growing a human isn't always possible. When you're pregnant and happen to be feeling anxious, exhausted, nauseous, achy or, you know, all the above, it can be really hard to appreciate the process of bringing a baby into the world. But one thing's for certain: Your body is achieving other-level feats of transformation, endurance and self-protection.

In fact, a recent study led by Duke University discovered that the amount of energy women use during pregnancy peaks around 2.2 times their resting energy expenditure. Top endurance athletes can get higher than that during shorter events like a marathon, but for an endurance "event" that lasts nine months, no one has ever burnt energy at a higher rate than pregnant people. In other words, juggling all the physiological demands of pregnancy pushes the body kind of like an ultramarathon—except this is one "race" you run every day for nine months instead of one or two days maybe ever.

"A pregnant body is working so incredibly hard during rest that the fact that it's also likely going to work, exercising and possibly already chasing children around is so incredible", says Ainslie Kehler, PhD, an exercise and reproductive health specialist based in Vancouver, British Columbia.

As many of the physiological changes that happen during those nine-ish months are internal, they may not be so obvious to you. So, to give you a better idea of how beyond your body is—even on days when you don't feel so hot—take a look at these almost inconceivable (get it?) events.

4 Surprising Ways Your Body Changes During Pregnancy

1. Your body develops a brand-new organ.

"Within the first 13 weeks of conception, the blood vessels of your uterus remodel themselves to help form the placenta, the only organ in the body that has a temporary lease", says Kehler. Its main job is to supply blood and nutrients to your baby as well as transport waste products like carbon dioxide out of your baby's blood. "It basically acts as a lung, a kidney and a complete digestive system for the growing baby", says Kehler. "It also produces hormones that help protect your little one from environmental toxins and infection", she adds. Best bodyguard ever.

2. Your blood volume nearly doubles.

"To make sure both you and your baby are getting enough nutrients and oxygen, the actual amount of blood circulating throughout your body increases during pregnancy", says Linda E. May, PhD, an exercise physiologist and a co-director at the Pregnancy and Infancy Research Collaborative at East Carolina University. (The other reason for the increase, according to Amanda Williams, MD, a board-certified obstetrician and gynaecologist in Oakland, California: to account for blood loss that happens during childbirth—yep, your body is smart enough to prep you with extra blood to spare!). "In fact, experts from the Mayo Clinic say that your blood volume can increase by 30 to 50 percent. For those carrying twins or triplets, that increase can be even greater", says Kehler.

"To pump all of this extra blood, your heart has to work harder. Stroke volume—the amount of blood your heart pumps per squeeze—increases each trimester, while your heart rate gradually goes up by 10 to 15 beats per minute", according to Kehler. As a result, the body's blood and oxygen flow boosts so much, it's enough to make some people blush. Literally. "That's one factor behind the 'pregnancy glow'", says Kehler. (TMYK!)

3. Your VO2 max increases.

Some of you runners may be happy to hear this: "The increase in blood and oxygen flow will also level up your VO2 max, the maximum amount of oxygen your body can consume during intense exercise", says Kehler. The higher this number is on your Speed Run, for example, the more oxygen you're able to use to produce energy and keep going.

"Increased VO2 max can last up to 12 months post-partum, which might (emphasis on might) make you feel faster and stronger during your workouts", says Kehler. "However, we need to weigh this possible 'advantage' against the fact that your ligaments have been under a lot of stress for nine-plus months, and many of your organs are still making their way back to their original spot", she adds. "Plus, docs typically recommend that you rest for a month or so after birth (or six to eight weeks if you had a C-section) before returning to exercise", says Kehler, which could make those first workouts back feel a bit tougher. "You might need to patiently build your cardio back up during your post-partum phase", says Kehler. No worries, though, that's what jogging strollers are for.

4. Your palate may change to help you get the right nutrients.

If you suddenly find yourself craving pickles and crisps but despising the rocket salads you used to love, your body may be trying to help you meet your nutritional needs. It's not totally clear why this happens, but scientists who performed one systematic review have some ideas. First, because you need extra sodium to support your and your baby's health right now, foods might seem blander to your taste buds, encouraging you to reach for the salt shaker. Second, the aversion to all things bitter could be a protective response, preventing you from eating harsh-tasting compounds that may (but probably won't) be toxic for you and the baby. Of course, these are just theories, but they're fascinating ones.


This is all to say, in those moments when you aren't feeling your best during your pregnancy journey, you may be able to ground yourself in the idea that your body is an amazingly intelligent powerhouse. Someone go get you a gold medal.

Words: Adele Jackson-Gibson
Photography: Vivian Kim

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