Exercise during Pregnancy

Basically, there is not a lot of research out there on exercise during pregnancy, for obvious reasons. It is not a comfortable (or ethical) state to study. I was very interested in this topic and did several presentations on it during my internship (first year of residency). The most recent ACOG (American College of Obstetrics & Gynecology) guideline (2002) is that in normal/non-complicated pregnancies (make sure that your doc validates that this is you), it is advised to moderately exercise (to keep your heart rate below 85% of your max heart rate which, is approximately 220-your age) up to 30 minutes per day on most days of the week.

ACOG recommends that after the first trimester, women should avoid full contact sports (soccer, tackle football, rock climbing, snowboarding, extreme cycling, etc). Most activities are safe, but those that pose a risk of abdominal trauma should be avoided. Activities that often recommend to my pregnant patients are swimming, cycling on a hybrid bike with seat and handlebars adjusted to an upright position to allow for good venous return to the heart, jogging at moderate intensity, yoga (this is fabulous in that it not only increases muscle tone and endurance but its benefit of increasing flexibility helps to preparing your hip and pelvic ligaments for childbirth). In contrast, scuba diving should be avoided not only due to an increased risk for traumatic abdominal injury, but also because the baby's immature circulatory system increases the baby's susceptibility to decompression sickness. Despite older traditional recommendations, running is ok but again, try to stay below 85% of your max heart rate.

It is also recommended to steer clear of weightlifting greater than about 15 pounds. The reason for this is that when lifting heavy weights, your body tends to forcibly exhale against a closed glottis, which increases intrathoracic pressure and decreases venous return to the heart (the technical term for this is the Valsalva maneuver). Under nongravid physiological circumstances, this is ok but in a gravid woman, this can potentially compromise oxygen delivery to your baby's developing organs.

Although there is inadequate research on strenuous exercise during exercise, athletes who continue to train at a moderate level during an uncomplicated pregnancy are considered safe. Different physicians have different ideas of what is safe but basically (as above) there is not concrete data on how much and how often a pregnant woman can safely exercise. So, most physicians make recommendations that they feel most comfortable with, and usually this means that they are following the most recent ACOG guidelines, detailed above.

In conclusion, if you are an athlete or a generally active person, you can continue to exercise but at slightly lower intensity during pregnancy. If you are not an athlete and do not exercise regularly prior to pregnancy, you are encouraged to begin an exercise regimen. This will absolutely make both you and your baby healthier. You should be reasonable about the new regimen. As in, start at 15 minutes three days per week and work up from there, not to exceed 85% of your maximum heart rate. Before beginning an exercise regimen (as always, even when not pregnant), you should check with your doctor to make sure that you are otherwise healthy (i.e. that you do not have a cardiovascular, respiratory, or any other abnormal health condition that could put and/or your baby at risk with increased activity).

Non-strenuous exercise during the postpartum period has been shown to reduce postpartum depression. Because it is known that weight loss at a moderate pace does not reduce the milk supply, it is safe to resume exercise while breastfeeding.