Running During Early Pregnancy: A Runner's Experience & Considerations

Question
Two days before I found out I was pregnant I ran 5 miles, in about 80 degree weather, for about 55 minutes.  The run occurred approximately 2 weeks after conception.  It was not humid, I had some water before the run, and I did not feel any symptoms of overheating like nausea or dizziness.  I have been running regularly for about 8 years, so I have a fairly high level of fitness. I am still very worried about this run. I did not realize the risks of associated with increasing your core temperature in pregnancy until recently.  I read that brain damage or neural tube defects can possibly result. What is the likelihood my core temperature increased to a dangerous level? Again, I did not feel overheated or sick, but I was warm and somewhat sweaty and it was around 80 degrees.

Answer
A lot, if most, of what you read on the internet about the risks of raising core temperature during pregnancy exercise is wrong.

Here are the facts:
First, pregnancy induces vasodilation, which increases cooling during exercise. Second, sweating increases for any given work load, also increasing cooling. Third, respiration rates increase too, which also speeds cooling. All of these pregnancy responses are directly fetal protective.

Core temperature rise in response to exercise is very small, usually less than 1 degree. Dangerous temperature rises are associates with levels above 102.

Since you are athletic, and well acclimated to a 5 mile run, you did not stress your system. This is why you did not feel overheated or physically taxed.

A dangerous rise in core temperature during exercise is highly associated with dehydration and high volume/high intensity workouts. Symptoms include fatigue, dizziness, nausea, pale clammy skin, and fainting. In cases like this, fluid intake, with electrolyte supplementation is necessary.

Pregnant women should always pay attention to hydration, avoid exercising in extreme weather conditions, and listen to internal body cues. Pregnant women should not go in hot tubs or saunas, or do "hot" yoga styles.

Most of the damage associated with rises in core temperature are flu related, especially in the fifth month. So frequent hand washing, and avoiding contact with infected persons are highly recommended.

You did not negatively impact your developing fetus. Keep up your athleticism. Fit moms give birth to healthier, stronger and even smarter babies, have easier pregnancies, with faster labors with fewer interventions, and bounce back more quickly. Better yet, fit, healthy moms raise fit, healthy children.

For more info on exercise during pregnancy go to: http://www.befitmom.com