After having a baby naturally or even through a C-section it is important to not force yourself to get back into shape. There are some exercises that you can do after having a baby to help strengthen your stomach muscles and start getting back into shape. However, putting too much strain and pressure on your body isn't good for you at all. This can actually cause more harm than good.
Doctors will clear a woman around 6 to 8 weeks after the delivery of a baby or have a C section. However, this doesn't mean that you can go out and start running, be jumping, or even doing leg lifts or crunches. This will damage your body. Your first exercises should be for breathing, walking, and other light exercises.
You are going to have to do special exercise to restore your core before you can get into heavy exercises like running, crunches or even leg lifts. You'll need to start with 2 exercise session each week and don't do them more than 15 minutes. The good exercises to do now would be:
The modified side plank
Bodyweight split squats
Band pull apart
You'll need to give your body plenty of time to heal before going off and doing more extensive exercises. When you are ready is when your body is ready and you'll be able to tell by examining the scar from the surgery. This normally will take 6 to 9 month to heal. But light exercise like the ones I've listed above will really help the healing process.