What determines an innie or outtie belly button?

Not necessarily.: An "outie" navel does not necessarily mean that you have an umbilical hernia. Ask your doctor to perform a physical exam to evaluate. If you do have a hernia, surgical repair is safe and effective. However, not all umbilical hernias need to be fixed. Those that are growing or causing symptoms should be fixed.

Navel: The navel is a scar where the umbilical cord was once attached. Around 90% of people have a depression (innie) ; about 10% have a protrusion (outie). It is reported that a protruding navel develops because of more abundant skin remaining after the umbilical cord is separated. However, it is still largely a mystery.