Blueflower, as long as you have been participating in those classes there is no need to stop, you'll just have to modify them as you get bigger. I did Pump till I was 38 weeks, Combat till I was 36 weeks and Balance till a few days before! Off the top of my head, Pump was the only class I had to make obvious changes for - raise the step at one end so you're not lying flat on your back, I also had trouble with the downward phase of the Clean & Press so when I got bigger I just did the rows. With Combat I just took the lower options, it's hard, especially if you're used to going flat out but it's better than nothing. So you walk instead of shuffling and keep the kicks low. In my Combat Manual it says the main things you need to watch out for are dehydration and hypoglycemia so have frequent sips of water before, during and after class and have small complex carb snacks before class.

Attack is the same, as long as you take the lower options and reduce your range of movement you can still do it. We have a pregnant woman in one of my Step classes and I have an instructor who taught up to 36 weeks but I, personally wouldn't do it becasuse of the risk of falling. Spinning is also good as you control the intensity.

Good luck with your pregnancy, you'll be amazed how quickly you'll bounce back this time if you continue exercising - everything was easier my third time round and i'm convinced it was becasue I was so fit.

Have fun!