During pregnancy, the womb gets much larger in order to make room for the growth of the baby. The womb pushes against the abdominal muscles, loosening and separating them. To correct this, a tummy tuck is necessary.
Along with trimming away excess fat and skin from the abdominal area, a plastic surgeon performing a tummy tuck is able to make changes to the underlying muscles. The surgeon can bring them closer together and suture them into place, creating a firmer abdominal wall.