I have pregnant patients who, if they gave up their physical fitness, would be denying themselves a very important aspect of their lives. Indeed, I feel a high level of fitness enhances their chances of success in labor and aids in their recovery.

Alas, our body does not understand exercise. When you are maxing out, and you are getting close to the edge of your abilities, your body is confused. It isn't responding as if this is something you want o do; your body can't believe you are doing this because you want to! Your body assumes you must be running for your life, being chased by a saber-tooth tiger or something. This is called the fight or flight response of the body, and when it occurs the body is just trying to survive. Blood is directed away from parts of the body that are not needed to survive. The bowel is turned off and the kidneys slow the production of urine. Blood is directed to essential organs; the heart, lungs, brain, muscles and the skin to cool the body. Unfortunately, the uterus is not a priority organ. When you are under great duress, at the point of maximum physical output, the blood flow to the womb can be decreased as much as 50%.

A study by a Dr. James Clapp, (yes, that's really his name and he is an Ob-Gyn) was undertaken in 1989 to see if these theoretical risks translated into real risks for the pregnant athlete. He looked at runners who ran 12 to 55 miles per week at intensities from 51-83% of maximum capacity to see if there was an increase in miscarriage or poor pregnancy outcome. It is not surprising that performance fell 14% over all the initial 8 weeks of pregnancy probably related to fatigue and nausea. Some women were forced to decrease their level of intensity because of shortness of breath or the sensation of a sudden increase in pulse rate.

The findings:

1) There was no relationship between miscarriage or pregnancy loss and the level of exercise in a pregnant woman.

2) There was no increase in the frequency of birth defects in the woman who exercised.

3) There was no increase in the frequency of premature labor or toxemia in the athletic women.

Now, before all my obstetric patients sign up for the Olympic marathon team, there are some things about this study that one must consider. First, there were only 141 athletes and 58 more sedentary individuals. This is not a huge number and it makes it difficult to look at fairly uncommon things like birth defects and make what we call statistically significant statements. Second, these women were very well conditioned at the time of conception and had been involved in these activities for a long time.

In summary, there is a theoretical risk to a pregnancy from an extreme level of exertion and in some animal studies this has been documented, but there is no objective evidence, as yet, in humans to prove there is an actual risk. The guidelines below are from the American College of Ob-Gyn, of which I am a Fellow. These guidelines are appropriate for the majority of women and can be used to safely maintain fitness throughout pregnancy.