Miscarriage and Exercise

I don’t know which pregnancy it was, but I had recently found out I was pregnant and because I am the biggest blabber mouth I know, I mentioned my new pregnancy to a middle-aged woman I didn’t know that well at church. After the meeting, we were putting away the chairs. She stopped me and took a chair away from me and said “you shouldn’t be lifting these.” It was embarrassing. I was even embarrassed for her because it dated her. The days of don’t lift anything, don’t walk more than a mile, don’t get your heart rate above 140 bpm as a flat guideline for every pregnant woman is gone. 

My first pregnancy, I was pretty clueless about everything about pregnancy so I had that archaic attitude. I thought pregnant woman were only allowed to walk for exercise. So that's all I did and kept on eating like I was running 5 days a week. I gained 70 lbs.

My second pregnancy, I must of read something about how we can do anything we were doing before. I was about 6 weeks pregnant and it was the first warm day we had that year, just before spring came. I went hiking with Jackson on my back (so carrying about 40 lbs). I was hiking on a new trail and it turned out to be the steepest trail I've ever found in my area. I got my heart rate up very high very fast and I got hot. Later that day I noticed that I had been spotting a little. This never happened with my first pregnancy so it freaked me out. 

Long story short, weeks of worrying, internet searches, internal debates about going into the doctor or not, my pregnancy ended at 11 weeks with a miscarriage. 

I know miscarriages can be absolutely devastating to women, but for me the emotions were disappointment with a whiff of guilt. I couldn't shake the thought that my exercising had killed my baby and then I miscarried. My doctor afterward said that it wasn't anything I did, that it was just a doomed pregnancy. He said it was a good thing--it showed that my body was fertile and doing what it's supposed to. 

I still had that guilt and fear when I went into my 3rd pregnancy. I didn't push myself hard at all. I biked because that was the lowest impact exercise I could do and still get my heart rate up a little. After the 1st trimester I picked up my effort a little, but by then I was so out of shape, I couldn't really do much. End result, I gained 60 lbs.

The goal for my third pregnancy is to gain the rcommended 25-35 lbs which I know I will only be able to do if I exercise daily. (I just love eating too much.) So, my question is: How much can I exercise during my pregnancy and not increase my risk of miscarriage? 

Hold on tight, I'm going to talk about research for a while. If you just can't stand it, skip down a few paragraphs where I'll give my take on the answer to this question.

There is one study, a danish study of about 92,000 women that found a 3.7 times increase in risk of miscarriage for women that exercised 7 hours a week compared to women that didn't exercise at all. Women that exercise half that much had a 2.2 times risk than a woman that didn't exercise at all. This was specifically for women 11-14 weeks pregnant, but the other gestational age groups also had greatly increased risk of miscarriage. I have seen this study referenced several times when you look up miscarriage risk and exercise. It was one of those studies that made the national headlines.

Here is the problem with the study: 1) By the author's own admission, the study has some bias and data collection problems. 2)The study did not take into account if the women were exercising prior to their pregnancies. 3)It did not take into account if the pregnancy was chromosomally normal. We know that 70% of miscarriages are due to a chromosomal problem of the pregnancy. No one caused it, it just happens. 

This study, however, took into account if the miscarriage was chromosomally normal. Of Chromosomally normal pregnancies, women that exercised had a 40% decrease in risk of miscarriage. This supports what my doctor said, that miscarriages are usually just doomed pregnancies and there is nothing I or any other woman did to cause it. 

This study did account for previous exercise and found that women who had been running or dancing before their pregnancies and continued to do so had no change in risk of miscarriage compared to women who just stopped exercising with their pregnancy.

This study and this study found protective affects of exercise against miscarriage. This study found no difference in risk.

 The only other study that showed an increased risk of miscarriage related to exercise found that strain or exercising more than normal during the time of implantation lead to an increase risk of miscarriage by about 2.5 times. 

With only a handful of studies that are saying conflicting things, more good research needs to be done.


 When thinking about my miscarriage, there are some stupid things I did. I wasn't in shape at all--the winter months tend to do that. Not being in shape isn't what was stupid, but going out and hiking with 40lbs on my back up a steep hill for the first time in months was. How quickly my heart rate and body temperature went up should have been a good indicator I was doing too much while pregnant.

 So to answer the question, we don't know yet and it is all relative. If you were doing nothing physically before trying to get pregnant, while you are trying to get pregnant and the beginning weeks of a pregnancy are not the time to start a running regimen. I read an article of an interview of elite runner Paula Radcliffe who ran 50 miles a week during her pregnancy. This, relative to her, wasn't that big of a deal because she was used to running 100 miles a week. 

Pregnancy isn't the time to push yourself hard to get fit fast; the goal should be to maintain some semblance of your fitness level before you got pregnant. This is why it is so important to get fit before you get pregnant.


Paula Radcliffe, Marathon world record holder racing (left) and running pregnant (right).