During the last nine months, the skin on your belly has been stretched to its limits. Now that your baby has arrived, your belly is smaller but, unfortunately, your skin is still stretched and saggy. Exercises can help tighten the loose skin to a point, but your most important weapon is time -- it took nine months to stretch your skin, and it will take several more for it to return to its pre-baby firmness.
Exercises that work the abdomen will not directly help you lose extra skin, but firming the muscles underneath can help tighten the overlying skin. Pelvic tilts and abdominal compression exercises can be done early on postpartum. Once you're fully recovered, you can try more intense exercises such as planks, bicycle crunches, side bridges and stability ball pikes.
Working your entire body with cardiovascular and strength-training exercises will build muscle and burn any excess fat that you have under your skin, causing your belly to appear more firm. Aim for at least 30 minutes of cardio most days of the week and strength train three times per week, focusing on exercises that target the major muscle groups in the body. Perform two to three sets of eight to 12 reps of each exercise.