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Running Sneakers and Baby Bumps

Running while pregnant vs. Dr. Google and random advice from strangers

Confession: I hate running.

But I like to stay in shape and running is the most convenient form of exercise for me so I lace up and run.

When I got pregnant with my first, I thought: “Sweet, now I have an excuse to stop running!” But, alas, the inner athlete in me refused to die with my expanding belly.

Running while pregnant falls into the same trap as most pregnancy “advice” (both solicited and unsolicited)—one person will say “you need to slow down!” and the next will say “didn’t so-and-so run a marathon when she was 8 months pregnant?” (Yes, she did)

The wide world of internet advice seems to stay a bit vague on this issue. More than once, I have seen or overheard the magic number of “140” (mom’s heart rate in beats/minute) floating around despite the fact that a little bit of investigation suggests that this recommendation was nixed in 1994 by the American College of Obstetricians and Gynecologists. But mostly, the advice is simple: if you are overheating, if you are throwing up, if you are bleeding or passing out, stop your workout. Seems a bit obvious to me.


if you are overheating, if you are throwing up, if you are bleeding or passing out, stop your workout.

Ok, on to the science of running while pregnant

A lengthy 2003 review in The British Journal of Sports Medicine scanned the data available throughout the scientific literature and found evidence (and lack of evidence) for the pregnant exercise dilemma.  The authors’ conclusion: 

Exercise has minimal risk and confirmed benefits for most women.

Did I fall into the category of “most women”? Not going to flatter myself, I probably did, but just in case, I dug further…

A 2012 study in the American Journal of Obstetrics and Gynecology categorized women into their exercise regiments and measured parameters of both mama and womb baby. Pregnant ladies ranging from 28-32 weeks were split into three groups: inactive, moderately active, and highly active. They were then tested before and after moderate and vigorous exercise (luckily for the inactive group, they weren’t pushed to the vigorous stage so this category only contains those who exercised a bit before the test). Measuring maternal heart rate (MHR), fetal heart rate (FHR), and indices of circulation making it between the two (via measurements from fancy Doppler sonography), the authors reached the conclusion that moderate exercise, even for the previously inactive pregnant ladies, does not change a single thing for the baby’s measurements. Only vigorous exercise caused changes—slight increase in FHR but a decrease in Doppler indices. interestingly, this decrease actually indicates improved circulation to the baby, making this change “not clinically significant.”


moderate exercise, even for the previously inactive pregnant ladies, does not change a single thing for the baby’s measurements.

What about pregnant elite athletes?

There’s a category that I definitely do not fit into:  elite athlete.  But just in case, I checked out an article entitled “Fetal Wellbeing May be Compromised During Strenuous Exercise Among Pregnant Elite Athletes”, a 2012 study The British Journal of Sports Medicine. However, I quickly lost attention when I realized that this study was conducted on SIX women and the only result they found (increased fetal heart rate) occurred when these Olympians, training for endurance events, were pushed to >90% of their maximal heart rate.

Basically, if you are training to run a marathon in 2 1/2 hours, you might want to shoot for a 3 hr pace instead when you are running for two.

I guess I don’t have to worry about that one.

In the end, I ran out of excuses so I laced up and headed out for the door. Bump and all.

(Epilogue: I stopped running around 28 weeks with baby #1 and 18 weeks with baby number two. Mostly because my big ‘ol belly felt like it was cutting off circulation to my lower half and my legs would go numb. Turns out there are comfort reasons to stop running while pregnant!)

For more information about the benefits of exercise during pregnancy and which activities to explore or avoid (looking at you pregnant SCUBA aficionado) – head over to ACOG’s page on the subject.


Want to learn more about health and nutrition during pregnancy? Check out our week-by-week nutrition guide for Mom and Baby!


This post was adapted from the original piece on

Photo credit: My very pregnant sister who put me to shame by running until she was 38 weeks pregnant.

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Molly Dickens, PhD

About Molly

Molly has her PhD in Physiology and spent over a decade as an academic research scientist slightly obsessed with the colliding worlds of brain science, hormones, stress and the reproductive system. Nowadays she heads up Content and Community at Bloomlife and edits Preg U. Science is still her jam and she can't help but continue to dive into the research world to find interesting bits about pregnancy and parenting.


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