Does your baby's bellybutton protrude when he or she cries? Don't be alarmed. This is a classic sign of an umbilical hernia — a common and typically harmless condition.

An umbilical hernia occurs when part of the intestine protrudes through a weak spot in the abdominal muscles. Umbilical hernias are most common in infants, but they can affect adults as well.

Most umbilical hernias close on their own by age 1, though up to 10 percent may take longer to heal. To prevent complications, umbilical hernias that don't disappear by age 4 or those that appear during adulthood may need surgical repair.