Kari,
I am a mother of three - I weighed between 115-125 at the start of
each pregnancy; I got up to 170 with the first two, and 180 with the
third. I always concentrated on many different ab exercises, but I
don't advise sit-ups. Find ab exercises that will be good to your
back too. My children are all grown now, but I still have a flat
tummy at 43.

I agree with Sean about yoga; wish I had know or thought about that
years ago.

Incidently, my daughter, Keri, just had her first baby 6 1/2 weeks
ago (my first grandchild). She is going to the gym 2-3 times a week,
and also practicing yoga. It seems to be helping; she has hardly any
tummy. She gained a lot in her pregnancy too (although not as much as
I had), and is gradually losing the extra weight with the help of the
Type A diet.

Hope this helps,
Sara

P.S. Congratulations!