I haven't gotten pregnant again, but I did ask about exercise as part of a discussion on managing a future pregnancy. My doctor said that she would tell me to continue doing whatever I was doing before pregnancy as long as it was comfortable. She told me not to over do it and to keep my heart rate under a pretty low limit compared to my age calculated maximum. She generally advises against starting new types of exercise during pregnancy or increasing intensity. My doctor did not put any restrictions on my non-pregnant activity and ordered me to get moving again when I had trouble losing the weight.
I exercised during my last pregnancy, and I noticed some pretty firm limits on what I could do. I was able to walk, swim, do pilates and prenatal yoga for most of it. During my second trimester, I biked and cross country skied a bit. I started having serious trouble with aerobic exercise after about 25 weeks, and I dialed it back pretty dramatically after that. Light exercise made me feel better and reduced my swelling when I could manage it.
The research on exercise and preeclampsia is inconclusive. While exercise has long-term cardiovascular benefits, it does not seem to offer any short term benefits during pregnancy. Several years ago, a British study found that really intense exercise in the first trimester increased the risk of severe PE. http://latimesblogs.latimes.com/booster ... nd-pr.html
I could not find any other studies that supported that result. A more recent study found that exercise reduces the risk factors for PE.http://scopeblog.stanford.edu/2011/10/1 ... eclampsia/
It seems that most doctors consider exercise as one of those things that probably doesn't hurt and probably doesn't help much. I think it really depends on how you respond to exercise (feel better or feel worse?) and what your doctor thinks about your particular situation.