The belly button, or navel, is a universal human feature, often categorized as either an “innie” or an “outie.” Its diverse forms stem from a specific biological process, rather than external influences.
The Umbilical Cord’s Journey
During pregnancy, the umbilical cord serves as a vital connection between a developing baby and the mother’s placenta. It contains blood vessels that deliver oxygen and nutrients to the fetus while removing waste products. The cord is encased in a protective gelatinous substance called Wharton’s jelly.
Once a baby is born, a healthcare professional clamps and cuts the umbilical cord, leaving a short stump attached to the baby’s abdomen. This stump typically dries and falls off within one to three weeks.
How the Belly Button Forms
The belly button is essentially a scar left behind after the umbilical cord stump detaches and the area heals. This healing process involves the formation of scar tissue, which is the primary determinant of whether a belly button becomes an “innie” (a depression) or an “outie” (a protrusion).
For an innie, the scar tissue typically retracts inward, pulling the skin to create a depression. If the skin and scar tissue protrude outward during healing, an outie forms. This outcome is largely a matter of how the skin naturally grows and the scar tissue settles, influencing the depth and overall shape of the navel.
Factors Influencing Shape
Several factors contribute to the final appearance of the belly button. The amount of remaining umbilical tissue can influence the shape, with excess scar tissue potentially leading to an outie. The way the skin and muscles around the navel grow and attach also plays a role, affecting how the skin folds and retracts.
The tension of the abdominal muscles around the navel can affect its appearance. Another significant factor is an umbilical hernia, where a portion of the intestine or abdominal fat pushes through a weak spot in the abdominal muscles. Such hernias nearly always result in an outie belly button, though they are generally harmless and often resolve on their own as a child grows.
Common Questions and Changes
Many common beliefs about belly button shape are not accurate. The way the umbilical cord is cut by a doctor does not determine whether a person will have an innie or an outie. Genetics are also not a primary determinant; it is mostly a matter of chance and the individual healing process.
While the initial shape is set by how the cord stump heals, a belly button’s appearance can change throughout life. Significant weight fluctuations can alter its depth and form as the surrounding skin and fat tissues expand or contract. Pregnancy can also cause an innie to temporarily or permanently become an outie due to the stretching of the abdominal wall. Additionally, certain abdominal surgeries can modify the navel’s appearance.