Incisional hernias occur when the abdominal muscle weakens as a result of a surgical incision. An incisional hernia can develop for a variety of reasons; individuals who engage in excessive or premature physical activity following surgery, gain significant weight, become pregnant, or raise abdominal pressure in any other way before the incision is fully healed are particularly vulnerable. Incisional hernias are most common three to six months after surgery, but they can occur at any time.