Unlike most hernias, which develop in adolescence or adulthood, 20 percent of babies are born with umbilical hernias. An umbilical hernia occurs at the umbilicus (belly button) when a loop of intestine pushes through the umbilical ring, a small opening in a fetus’ abdominal muscles through which the umbilical cord-which connects a fetus to its mother while in the womb-passes. Umbilical hernias occur most often in newborns, and 90 percent will naturally close by the time the child reaches 5 years of age.