Answer from Gail Akers: The American College of Obstetrics and Gynecology are constantly updating their guidelines for exercising during pregnancy. Some important guidlines are that you should not be doing anything in a supine (on your back) position after the first trimester, heart rate should not exceed 140 beats per minute and do not start a new exercise program when you conceive.Please do check with your ob/gyn for the latest updates /guidelines ( they do change). Most ob/gyn's will allow for exercise if you have doing it well before conceiving, however, it will also depend on the course of your pregnancy, whether it becomes a high risk, etc...