An umbilical hernia in an infant is caused by the incomplete closure of the umbilical ring (muscle), through which the umbilical blood vessels passed to provide nourishment to the developing fetus.

The hernia generally appears as a soft swelling beneath the skin that often protrudes when the infant is upright, or with crying or straining. Depending on the severity, the area of the defect can vary from less than 1 to more than 5 centimeters in diameter.

Small (less than 1 cm) hernias usually close spontaneously without treatment by age 3 to 4 years. Those that do not close may require surgery. Umbilical hernias are usually painless.

Umbilical hernias are common in infants. The exact incidence is unknown, but may be as high as 1 in 6 infants.

Umbilical hernias occur slightly more frequently in infants of African American descent. The vast majority of umbilical hernias are not related to any disease condition. However, umbilical hernias can be associated with rare diseases, such as mucopolysaccharide storage diseases, Beckwith-Wiedemann syndrome, Down syndrome, and others.