A hernia occurs when the abdominal wall's muscle or tissue has a defect, which allows abdominal contents, usually bowel, to push through.
Many babies are born with a specific type of hernia at their belly button. Called an umbilical hernia, they appear to have a pouching out of the navel, which gets bigger when crying or straining and smaller when relaxed. They can appear small at first and increase in size for the first month or so of life. It’s called umbilical because it is located at the umbilical fibromuscular ring. This ring is a normal opening in babies and usually closes completely by age 2, so this type of hernia is uncommon after infancy. As long as it remains soft and not tender, there is nothing to worry about.