You should consult a physician about that. Don't take advice from anyone on here. To my knowledge you shouldn't do any abs while in your second tri. I've heard speed walking is the best exercise while your pregnant. But then again I am not a dr. Good luck. And congratulations.
I do alot of walking when I was pregnant with 3 of my kids. It will help u out when u give birth to the baby. After u have baby, wait 6 weeks before u start exercising.