Docs debate pregnant women’s safety

By Scott Douglas

At last year's Chicago Marathon, Amber Miller finished in 6:25:50 despite being 39 weeks pregnant. That evening, she gave birth a healthy girl. By all accounts, Miller and her child suffer no repercussions a year later. Does this mean marathoning and late-term pregnancy are a good fit?

That's the topic among physicians and exercise scientists in a recent issue of the Journal of Applied Physiology. On the one hand, two marathoning doctors point out that, at an average pace of about 6km per hour, Miller was more walking than racing. (Miller mixed walking and running during the marathon.) In addition, despite the heat at last year's race, Miller was able to hydrate at will, and she stopped to eat occasionally. As such, "it can be assumed that she did not have exertional hyperthermia (core temperature >40°C) post-finish, nor did she become hypoglycemic," they write.

Indeed, the doctors write, "from a physiological standpoint of the mother and fetus, we affirm that walking at a brisk pace to complete a marathon in over 6 hours in temperatures that ranged between 14 to 26°C, while keeping adequately hydrated and nourished, was, in our opinion, 'not that big a deal.'" (So there!)

On the other hand is the contention that because something can be done doesn't mean it should be done.

"In pregnant women with a cervix ready for delivery, exercise induces uterine contractions that may not be perceived by the exercising woman," a Dutch physician writes." During uterine contractions, [uterine blood flow] decreases in proportion to the intrauterine pressure increase, not negligible in humans. The combined reduction in [uterine blood flow], induced by contractions and exercise, has not been quantified."

This doctor concludes that Miller's marathon/giving birth double "should be taken as proof of concept rather than as proof of safety."

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