Exercise in pregnancy

So, with each of my pregnancies, I have exercised before I got pregnant and then stopped while I was pregnant. A big part of it has been the fatigue you feel during those first 3 months. With Taylor, I did walk about 3 miles a day until I was in the 3rd trimester, but that was when we moved from KS to ND and it just was not warm enough to walk outside anymore. This time, I didn't do anything until about 20 weeks and was good about walking on the treadmill for a week or two. Now, I have walked at least a mile, if not 3 everyday this week. I am planning to continue for the duration of my pregnancy.... until the naps outweigh the workouts. :o)