Marathon Running During Pregnancy: Safety and Considerations

Question
Hello,
I have been distance running for roughly four years. I have been training for a marathon and recently found out I am pregnant. I am four weeks pregnant. At the time of the marathon I will be roughly 8 weeks. I have no risk factors related to my pregnancy at this time. I had already completed the longest of my training runs before I found out I was pregnant (the longest was 20 miles). During my training for this marathon (it will be my third marathon) I have not been logging as many miles a week as I typically would have due to an old leg injury, but I have completed all my long runs each week. So my question is, is it safe for me to still run the marathon?
Thanks

Answer
Generally, it is safe for a woman to continue with whatever level of physical exertion she is acclimated to during the first half of pregnancy.

You should know that one (and only one) meta-analysis study done in Europe has found a small correlation between high impact/high intensity/high volume exercise and first trimester miscarriage. Certainly marathon training falls into this exercise category.

But, at this point we don't' know why this one study has found a link, or whether there are other factors, such as chronic over-training, nutritional depletion, etc. that might have a causal effect.

Pregnancy increases blood volume and metabolism, and so your body is doing more work, even while at rest. For some women, this increase in basal workload, on top of intense training might push one into an over-training mode. General fatigue, reduced strength during exercise, reduced coordination, and poor sleep are often first indicators of over training. But trained athletes are often very good at "pushing through the pain" and not paying attention to their body's negative signals.

I suggest that you monitor your resting heart rate. Take you HR, for a full minute, first thing in the morning, before you get out of bed. Then sit up on the side of your bed, feet/knees over the edge and after 30 seconds or so, then take your HR again. If the second number is more than 10 beats per minute over your supine HR, then you may be over taxing your body. Certainly, if this happens, I suggest that you do not run the marathon.

But if you have no indications of over training, then it's a judgment call on your part. If running the event will not cause you increased psychological stress, then you may want to go ahead, but if it will cause worry that may linger for the rest of your pregnancy, then why do it?

Sorry that I can't give you a black and white answer your question.