The navel, or umbilicus, is the body’s most common and universally recognized scar, marking the former attachment point of the umbilical cord. For many, the appearance of this scar remains static throughout life, but it is common for its shape to change over time, often shifting from a protruding “outie” to an inverted “innie.” This transformation is usually the result of normal anatomical shifts occurring within the abdominal wall and surrounding tissues. Understanding the structure of the navel helps explain why it is susceptible to changes in the body’s internal landscape.
Understanding Navel Shape
The initial shape of the navel is determined by how the scar tissue forms after the umbilical cord stump falls away shortly after birth. This process is natural and is not influenced by how the cord was clamped or cut. An inverted navel, or “innie,” occurs when the skin adheres cleanly and retracts inward to the abdominal wall underneath. This inward adhesion is the most common outcome, with an estimated 90% of the population developing an innie.
A protruding navel, or “outie,” results when the skin and scar tissue do not retract fully, instead remaining slightly projected outward. This projection is typically due to a small excess of scar tissue, or sometimes a minor weakness in the abdominal muscle wall near the navel. In most instances, this minor protrusion is cosmetic and represents a normal variation in human anatomy. The navel’s attachment to the underlying fascia makes it responsive to internal abdominal pressure and changes in external tissue distribution.
How Body Composition Alters Navel Appearance
The most frequent explanation for a navel changing from an outie to an innie involves shifts in abdominal body composition. The appearance of the navel is heavily influenced by the amount of subcutaneous fat, the layer situated just beneath the skin. When an individual gains significant weight, the accumulation of this fat stretches the overlying skin outward. This stretching effect can flatten a previously protruding outie navel, or cause the surrounding skin to create a fold that pulls the scar tissue inward, converting it into an innie.
Conversely, losing a substantial amount of weight can also induce a change in the navel’s appearance. As body fat is lost, the abdominal skin may lose its tension and elasticity, especially after dramatic weight reduction. This reduction in volume can cause the skin to sag slightly, pulling the central scar tissue deeper into the abdominal cavity, thereby accentuating the “innie” appearance. Changes in visceral fat and the strengthening or weakening of core abdominal muscles can alter the internal pressure exerted on the umbilical area, contributing to the shift in shape.
The Impact of Pregnancy and Aging
Major life events like pregnancy and aging cause structural changes to the abdomen that are distinct from general weight fluctuations. During pregnancy, the expanding uterus exerts outward pressure on the abdominal wall, often forcing an innie navel to “pop” out and become a temporary outie. After childbirth, the abdominal wall and skin retract, but the extreme stretching can diminish the skin’s elasticity and lead to a permanent change.
Postpartum healing can result in the stretched skin settling in a flatter position, or the residual tension causing the navel to flatten and invert more deeply than before, resulting in a permanent innie. Aging also contributes to navel changes through the gradual degradation of structural proteins. The body produces less collagen and elastin, which reduces the skin’s ability to maintain its original contour. This loss often causes a once-prominent outie to sag and flatten inward over time.
When a Changing Navel Needs Medical Attention
While the conversion from an outie to an innie is usually a harmless, cosmetic event driven by natural anatomical shifts, specific circumstances warrant medical consultation. The primary concern is the possibility of an umbilical hernia, a condition where tissue pushes through a weak spot in the abdominal muscle near the navel. A small, soft outie can sometimes be a minor hernia, and if it suddenly flattens into an innie, it is usually not a concern.
Immediate medical attention is necessary if the change is abrupt and accompanied by pain, tenderness, or a feeling of pressure. Attention is also needed if the navel area becomes firm, discolored, or hot to the touch. These signs, or systemic symptoms such as nausea, vomiting, or an inability to pass gas or stool, could indicate a serious complication, like an incarcerated or strangulated hernia.