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.

Activities that I often recommend to my pregnant patients are swimming, cycling on a hybrid or mountain bike with the handlebars adjusted to an upright position (this allows for effective venous return to the heart), jogging at moderate intensity, and yoga. Yoga, in particular is fabulous for pregnant women; the benefits of improved muscle tone, endurance, and flexibility will make both childbirth and child rearing much easier. The improved flexibility derived from regular prenatal yoga practice will prepare your hip and pelvic ligaments for childbirth. Despite older recommendations, running is ok but again, you should try to stay below 85% of your max heart rate.

ACOG recommends that after the first trimester, women should avoid full contact sports (soccer, tackle football, rock climbing, snowboarding, extreme cycling, etc) due to the risk of abdominal trauma.  Any sport that relies strongly on balance such as dancing, biking, and snowboarding (also considered a contact sport unless you are VERY advanced) should be performed with caution; as your baby continues to grow, your center of gravity gradually shifts away from what you are used to.Without caution , a sport that would otherwise be 'non-contact' can quickly become a 'contact' sport and can lead to a painful and potentially dangerous fall for both you and your baby.

Despite inadquate research in this area, it is thought that athletes who continue to train at a moderate level during an uncomplicated pregnancy are considered safe. Because there is no concrete data on the amount, intensity, or duration of exercise that is 'safe' for a pregnant woman, you will most likely hear differing opinions from different providers.  The most up to date guideline however is that a healthy female with a normal, uncompicated pregnancy can safely exercise with proper caution detailed above.

In conclusion, if you are an athlete or a generally active person, you can continue to exercise during your pregnancy, with more caution and slightly lower intensity. If you did not exercise regularly prior to pregnancy, you are encouraged to begin an exercise regimen. 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 (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). Beginning an exercise regimen during pregnancy will absolutely make both you and your baby healthier. You should be reasonable and cautious with your 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.

Non-strenuous exercise during the postpartum period has been shown to reduce postpartum depression. Postpartum weight loss at a moderate pace has not been shown to cause any reduction in milk supply.

So...get out there and move your body...have fun and be safe!