Umbilical hernias are bits of tissue that protrude through the umbilical opening. Some hernias in young puppies will go away on their own within a few weeks or months, though if one is still present by 5-6 months of age it isn’t likely to change without surgery. Sometimes the opening in the abdominal wall is very small, so what you see pushing through is only a bit of the fat that lines the interior of the abdomen. The wall may actually have closed, isolating a small pad of fat under the skin. Large openings pose a danger to the dog due to the risk of a loop of intestine slipping through and becoming strangulated. This requires surgical correction and these dogs should not be bred.
There is a persistent myth that hernias are caused by the dam tugging on the umbilical cord at birth. This is not true. Umbilical hernias are inherited and should be considered faulty. Dogs with minor hernias might be bred but not to mates who have umbilical hernias or who have close relatives that have them. Males with hernias should not be used extensively.
Hernias in other areas than the umbilicus are not known to be inherited.