Hey L.,
I agree with Carey S. You should speak with your doc first. I have to say, though, that what has been good for other moms, isn't necessarily what will be good for you. I exercised when I was preg too, but I kept it a sensible speed walk, with arm weights. In general, as long as the baby isn't being toussled around (running), you can contiue to exercise. Yoga is great, as you did with your first. I just don't think that running is a good thing when pregnant, unless (maybe) if it's your first, and young, and have been running as part of a normal routine. Of course, all moms are different. This website is great to get some insight, but I think that there is a sense of intrusion when it comes to things like this. The only people who you should listen to (regarding your pregnancy, and your health) should be you, your doc, and your spouse. Pregnancy isn't something that works the same way every time with your own pregnancies, let alone anyone elses. I will say this...I was in excellent shape with my first, I exercised every day as usual (removing all high impact stuff). I didn't feel any problems, but she was born 4 weeks early, and because I was unusually small, she was also born very preemie. I still walked with my 2nd and third kids, but nowhere near as with my first. Just regular steady pace walking, no weights, for about 30 min. It kept me at a steady weight. :o) Just do what U, your doc and spouse think is ok for you.
Good Luck!
M.