The human belly button, or navel, is a unique feature on the abdomen. It marks where the umbilical cord connected a developing fetus to its mother, providing nourishment. After birth, the cord is cut, and the remaining stump falls off, leaving a scar that becomes the belly button. While most people have an “innie” navel, a depression, a smaller proportion have an “outie,” where the skin protrudes outward.
The Frequency of Outie Belly Buttons
Outie belly buttons are less common than innies, but they are far from rare. Approximately 10% of people have an outie belly button, meaning millions worldwide have one. The appearance of a belly button is largely a matter of how the skin heals after the umbilical stump detaches.
Belly Button Formation and Outie Causes
A baby’s belly button forms from the healing process of the umbilical cord stump. The umbilical cord, which linked the fetus to the placenta, is cut shortly after birth, leaving a small stump. This stump dries and typically falls off within one to two weeks, leaving a scar. The final appearance of the belly button, whether an innie or an outie, depends on how this scar tissue forms and how the skin around the navel heals.
Outie belly buttons usually result from natural variations in this healing process. Sometimes, extra skin or scar tissue protrudes instead of retracting inward. The way the umbilical cord was cut or clamped does not determine if a person will have an innie or an outie; it is primarily influenced by how the cord site naturally heals and the scar’s shape. Genetic factors can also influence an outie.
Outies and Health Considerations
While most outie belly buttons are a normal variation, some may indicate an underlying medical condition. One such condition is an umbilical hernia, which occurs when a portion of the intestine or abdominal fat pushes through a weak spot in the abdominal wall near the navel. This can cause a soft bulge around the belly button that may become more noticeable when a baby cries or strains. Umbilical hernias are common in newborns, affecting about one in five, and often close on their own by age one or two.
Another cause for an outie can be an umbilical granuloma, which is a small mass of inflamed tissue that forms at the site where the umbilical cord fell off. This may appear as a pinkish or reddish area, possibly oozing yellowish fluid. Granulomas are typically harmless and often resolve without intervention. However, certain signs and symptoms warrant medical attention, such as persistent redness, swelling, increased pain, or foul-smelling discharge from the belly button. Prompt medical evaluation is also needed for a bulge that becomes tender, discolored, or causes vomiting.