I think its different for everyone and depends alot on how your labor and delivery went. I had a c-section and my doctor okayed me to resume working out after four weeks, but asked me to wait a little long before doing abs. It also depends alot on how you feel, like if you are getting enough sleep or not (ha,ha,). Also I find its very hard sometimes to find the time to workout when you have a newborn.
Good luck to you and your pending arrival. I hope you have a fast and easy delivery!
Linda (son born 10/03/01)