fatpony - I stopped running, partly because I had a DVT in my left leg, so Drs expect that pregnancy is going to cause some vein issues that pounding exercise will make worse. I'm now on a cross trainer, and for half the amount of time. I've been going to pump classes, but on smaller weights, particularly for the back stuff, and I don't do the abs at all (gym bloke said not to, and so did the pump teacher).
My normal gym routine is all on legs, shoulders and some upper back stuff. He seemed to think that legs were particularly important - squats etc, which I'm pretty happy with. I have a feeling I'm going to be a walker and a squatter in labour if I can, so need to keep my legs strong. The back stuff is about core strength - I've had one change since I started there, initially it was lower back strength, then upper back. But I've been doing a mixture in pump classes anyway. Shoulders and upper arms are good ones to keep going just because different exercises seem to define you quite quickly, which I reckon will be good for self esteem stuff as the rest of the body goes 'wrong'.
I've also been swimming. I had a lesson with a guy who is a tri type, who gave me a training routine to follow. It's about intervals really, so some as fast as you can go, some slow stroke etc. I had the lesson to improve my front crawl, since I tend to resort to breast stroke, especially when tired, and I think that won't work for my back later on - my back already hurts sometimes from breast stroke.
So, I'm swimming 3 mornings a week for about 45 minutes, going to two 45 minute pump classes, use the gym once or twice a week, and going to a body balance class once a week (too boring to do more often than that) if I can get into one (they fill up quick at my gym). I've been tired for some of it, so just slacken off a bit, but still do the movements.
I'm already overweight (hard to believe with that exercise innit.. grrr), but don't want to put too much on.