What causes an innie or outie bellybutton?

The innies, the outies and the in-betweens. Of course we all know the different types of belly buttons out there, but does anyone really know why we are the way we are? How is it that some people have that little extra piece of skin protruding out while others have a little hole?

Our belly buttons all start off the same way: as an umbilical cord waiting to be cut and have the remains fall off forming what we know as the belly button. About 90% of bellybuttons are innies, while the other 10% are outies. It is a believed theory that the way a doctor handles the umbilical cord can influence how a belly button will develop. Doctors clamp several inches of the umbilical cord from the body and once that falls off, the remaining piece cannot be manipulated or surgically changed. Perhaps there is a certain distance of clamped UM cord that is more likely to create an outie or vice versa. Since there is no evidence to prove this true, we cannot assume that this correlation equal causation. There is always a possibility that events are due to chance and with this topic of belly buttons, it could possibly be that outie bellybuttons are more rare and are a product of chance.


Dr. Cetrulo from a hospital in Boston does not agree with the theory of doctors influencing the belly button outcome. He explains that the outcome of a bellybutton is due to the space between the skin and the abdominal wall. He claims that, “if the soft tissue protrudes though, you’ve got an outie”.

I’m not sure what type of experiment could be tested to try and determine the cause of the bellybutton. The information we have provides an observational outlook of the topic.

As no one has control over what type of bellybutton a child will develop, it is hard to determine what causes either kind. While there are a larger percentage of people with innie bellybuttons, there is just about an equal chance of receiving other. You never know!





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