The navel, or umbilicus, is a unique scar left from where the umbilical cord once connected a person to their mother. The terms “innie” and “outie” describe the final shape of this scar tissue, which is either inverted (innie) or protruding (outie). An innie is the far more common type, but the appearance is ultimately determined by the natural healing process. Significant physiological or structural changes to the abdomen can indeed cause an innie to become an outie later in life.
The Anatomy of the Navel
The appearance of the navel is a direct result of how the abdominal wall heals after the umbilical cord stump falls off shortly after birth. This spot is defined by the umbilical ring, a dense, fibrous fascial scar that closes the opening where the umbilical cord passed through the abdominal muscles. An innie forms when the skin and underlying scar tissue adhere firmly and retract slightly inward.
The inverted shape is also influenced by the amount of subcutaneous fat surrounding the area, which causes the skin to fold inward. Conversely, an outie results when the residual scar tissue protrudes slightly outward, or when the skin has a less firm adhesion to the underlying tissue. This structure is a weak point in the abdominal fascia, making the navel susceptible to changes in internal pressure.
Primary Drivers of Navel Shape Change
The most common reasons an inverted navel begins to protrude are related to a significant increase in intra-abdominal pressure. This pressure stretches the abdominal wall, forcing the skin and connective tissue at the umbilical ring outward. The two primary, non-pathological drivers of this change are pregnancy and substantial weight gain.
During pregnancy, the rapidly growing uterus pushes abdominal contents forward. In the third trimester, this outward pressure often causes the navel to evert, temporarily turning an innie into an outie. Similarly, a significant accumulation of visceral and subcutaneous fat increases the volume and pressure inside the abdominal cavity, pushing against the fascial ring and causing protrusion.
When a Change Indicates a Medical Issue
While pressure from weight gain or pregnancy is purely physiological, a change from an innie to an outie can also signal a structural defect known as an umbilical hernia. This condition occurs when the umbilical ring develops a weakness or a small opening. This allows a portion of internal tissue, typically abdominal fat or a loop of intestine, to push outward.
The resulting protrusion is generally softer to the touch and may become more noticeable when the person strains, coughs, or stands up. Unlike the simple stretching seen in pregnancy, a hernia represents a breach in the fascial layer of the abdominal wall. A persistent, painful, or tender protrusion that cannot be gently pushed back in requires immediate medical attention to prevent complications such as tissue strangulation.
Reversibility and Long-Term Outlook
The long-term outlook for a shape change depends entirely on its underlying cause, which determines the reversibility of the protrusion. For changes caused by pregnancy, the majority of navels revert to their original inverted shape in the months following childbirth. However, the skin and connective tissue may remain slightly stretched, occasionally leaving the navel wider or shallower.
Navel eversion due to generalized weight gain often resolves with significant weight loss, as the reduction in fat decreases the intra-abdominal pressure. Conversely, an umbilical hernia involves a structural gap in the abdominal fascia and will not correct itself in an adult. Surgical repair, or hernioplasty, is required to close the defect and restore the original shape.