An umbilical hernia is an outward bulging (protrusion) of the abdominal lining or part of the abdominal organ(s) through the area around the belly button.
A hernia can vary in width from less than 1 centimeter to more than 5 centimeters.
There is a soft swelling over the belly button that often bulges when the baby sits up, cries, or strains. The bulge may be flat when the infant lies on the back and is quiet.
Follow Yahoo Health on Twitter and become a fan on