“What are your opinions about running and pregnancy. Does it affect it does it hurt the baby in the beginning trimester? Does it affect trying to get pregnant? There are so many myths out there. I have been training for a half marathon for the past year and have a good base of ten miles and have run 3 half marathons, everyone tells me to stop if I want to get pregnant, but I feel like I already have a good base so its not like I am overworking myself to the point of exhaustion. Any tips you have I’d love them.”
As a rule, pregnant women are encouraged to engage in regular, moderate intensity physical activity. You are correct, however, in that there are many myths surrounding exercise and pregnancy. This is partly due to the scarcity of data on the subject and the ever changing positions from the American Academy of Obstetrics and Gynecology over the years. Some of the original concerns were theoretical. These included a fear that rising a woman’s body temperature, as occurs with exercise, can cause birth defects in the developing baby particularly in the first 3 months (first trimester). This concern was based on studies done in mice in which increases in body temperature resulted in deformed or miscarried babies. This has never been proven in humans although, as you can imagine, such a study would be difficult to find volunteers. Body temperatures between 102 and 103 degrees Fahrenheit can be reached in normal modest to intense exercise under normal conditions without harm to a developing baby. Another myth associated with exercise was the fear that active muscles demand increased blood flow, blood flow that could be taken away from or stolen from the baby and placenta. This also has never been proven under typical exercise conditions. Lastly, is the fear that the excess jostling that occurs with exercise could be harmful to the baby. This may be true for situations in which the mother is exposed to major trauma e.g. motor vehicle accidents or falls, but is not true for typical non-contact exercise in an otherwise normal and uncomplicated pregnancy.