Hernias occur when an organ or tissue pushes through its usual space; they can be present at birth or develop as time passes. Umbilical hernias occur when fat, fluid, or intestine pushes into the abdominal muscles. In order to correct the hernia, the doctor makes an incision in the abdomen, and moves the intestine or fat back into its normal place. Mesh is also sometimes inserted to strengthen the abdomen. Umbilical hernias in children may heal on their own, while in adults, the hernias should usually be treated.