While almost every human is born with a single belly button, or umbilicus, having two is biologically possible under specific, extremely rare circumstances. This unusual condition is documented in medical literature, distinguishing it from other similar-looking skin features. The existence of a second navel relates to anomalies in early abdominal development.
The Formation of a Single Navel
The navel is a physiological scar, the first scar a human acquires. It forms following the severance of the umbilical cord at birth, which connected the fetus to the placenta during gestation. The cord passes through an opening in the abdominal wall.
After birth, the cord is clamped and cut, leaving a small stump that naturally shrivels and falls off within a week or two. The resulting wound heals through a natural scarring process. This process closes the opening in the abdominal wall and forms the depression or protrusion known as the belly button.
The Rare Condition of Accessory Navels
The phenomenon of having two or more belly buttons is a congenital anomaly known medically as Polyumbilicus, or supernumerary umbilicus. This condition is exceptionally rare, with only a small number of true cases documented in medical literature. A true accessory navel is distinct because it features the histological components of a normal umbilicus, including the presence of an umbilical ring and an underlying fibrous cord remnant.
The anomaly is thought to result from errors during the complex process of abdominal wall development in the early stages of fetal growth. A flaw in this process can sometimes lead to the formation of multiple or displaced umbilical structures. This developmental error can range from a fully formed, though usually smaller, secondary navel to a small depression, skin tag, or a pigmented patch of skin.
In many documented instances, the accessory navel is located on the midline of the abdomen, either above or below the primary navel. A true accessory navel is generally benign and does not typically pose a health risk. Due to its extreme rarity, it is most often identified incidentally during a physical examination.
Distinguishing Similar Skin Features
Many people who believe they have a second belly button are actually observing other common skin features that resemble a navel. Accessory nipples, known as polythelia, are often mistaken for secondary navels, especially when they occur on the abdomen. Extra nipples form along the embryonic milk lines, which run vertically from the armpit down to the groin, and their appearance can vary from a small mole-like spot to a fully formed nipple.
Surgical scars are another common source of confusion, particularly those resulting from procedures like laparoscopy or abdominoplasty. Laparoscopic surgery often involves a small incision at the navel, or a second tiny incision elsewhere on the abdomen, which can heal into a circular depression that mimics a small umbilicus. In a tummy tuck procedure, the surgeon creates a new opening for the original navel, and the resulting scar tissue can sometimes look like a separate feature. A medical professional can easily differentiate these common skin features and surgical marks from a true accessory navel.