I have just got this off the net.???
Most umbilical hurnias are hereditary however you can get a swelling without the hernia from the bitch pulling at the cord,if the hurnia reduces when you rub it gently and you can feel a small hole inside then it will probably be inherited if however the swelling does not reduce then the hole in the abdominal wall is closed it should never cause the dog a problem and is most likely caused by the bitch being a bit too attentive.And if it is a hereditary hernia they should not be bred from..
Hope it helps? ?