Here’s what Professor Hallux has to say:
Do you know which sort you have? An “innie” goes in and is like a crater – an outie sticks out a bit – it’s more like a button. You’ve just had a quick look to check, haven’t you! It all starts in the womb when the baby is joined to the mother by a stretchy cord called the umbilical cord. When the baby is born the cord is cut.
Some of the baby’s skin, from his or her tummy will be covering part of the cord – and the more skin there is on the cord, the more likely it is for the baby to have an outie. It can depend on the muscles in mum’s tummy too. Most people on the planet have an innie – nine out of every ten people in fact!
So if you’ve got an outie – consider yourself pretty special!