An umbilical hernia occurs when part of the intestine protrudes through an opening in the abdominal muscles. Umbilical hernia is a common and typically harmless condition. Umbilical hernias are most common in infants, but they can affect adults as well. In an infant, an umbilical hernia may be especially evident when the infant cries, causing the baby's bellybutton to protrude. This is a classic sign of an umbilical hernia.
Many umbilical hernias close on their own by age 1, though some take longer to heal. To prevent complications, umbilical hernias that don't disappear by age 3 or those that appear during adulthood may need surgical repair.