I'd check with your doctor or OB about it.

Exercise is good and healthy in pregnancy. It's good for you to continue with stuff that you were doing before, as long as you don't push your body too much, and pay attention to how you feel. If you are feeling fine with it, and the exercise isn't something too dangerous (horseriding is out, for example, due to the risk of falls) it shouldn't be anything but good for you and the baby.

I've recently stopped my cycling (at 24 weeks), because I got too worried about the potential of falling off, now that my sense of balance is getting weirder by the day. But I plan to make up for that with more swimming from now on - you can't fall off a swimming pool!