What do you do for a herniated umbilical cord in a baby? why does it happen in the first place?

Confusing question: If your ? Is about a umbilical hernia in an infant, the response depends somewhat on the size & age of the infant. They are common & most self heal as the child's abdominal muscles become stronger with age. By 1-2 yrs most have disappeared. Those that are very large or tend to trap intestinal contents may need to be fixed, but most will wait to see if the improve with age.