I do aerobics type classes about 3 times a week (not lately though, I've been lazy!!). I certainly wouldn't stop just because of ttc, they say the healthier you are the better. I personally can't see any real risk in this at all but you have to do what you're comfortable with. If you're at all worried, maybe talk to your doctor for reassurance.
To be honest, I think we worry about too much and overthink ttc and I really don't think exercise is a problem
