I do yoga and a lot.of walking n stretching and its.kept my weight gain right where it needs to be. I plan on picking up swimming asap as well
Anything not strenous and not targeting abs area. Walking is good, swimming wonderful aerobics and resistance training but low impact unless you have been doing them prior to pregnancy.
Or you could try stair master!
I just walk a lot it's a lot harder for me now because baby lays so low but I think walking is great
at your stage pretty much any normal workout is safe, I wouldn't do any heavy weight lifting or anything too extensive though