its a medical mystery. However, read on wisegeek that it has to do with the way it heals once the umbilical cord is severed at birth.
umm no not really... i have an outie and its not sensitive
why some have depressed navels while others have protruding navels.
Around 10-20% of the population have outie bellybuttons, which are protruding rather than concave. The shape of a person's bellybutton is determined by how the umbilical cord heals after birth.
Well most professional body piercers won't pierce "outie" navels because of the irritation the piercing will be subjected to. This generally leads to migration and rejection. Find something else to pierce.
she has a outie
Outie. Looks like a full gumball sphere outie!
Outie
The Woman Who Had Two Navels was created in 1961.
A small knob outie.
He has an little outie belly button.
samba.. it was just on jepordy
Very shallow innie. It was an outie when he was a kid but sunk in a little as he got older. It sinks in when he gains weight but pokes out when he has abs. With enough pressure, it could pop back out to a full outie again.