An outie belly button is not directly inherited from your parents the way eye color or hair texture is. No single gene determines whether you end up with an innie or an outie. Instead, your belly button shape is primarily the result of how the tissue around your umbilical cord heals after birth, along with a few anatomical variables that may have a partial genetic component. About 10 percent of people have an outie, while the vast majority have innies.
How Your Belly Button Actually Forms
During pregnancy, the umbilical cord connects through a small opening in the baby’s abdominal wall muscles called the umbilical ring. After birth, the cord is clamped and cut, leaving a short stump attached to the baby’s belly. Over the next one to three weeks, that stump dries out, shrinks, changes color from yellowish-green to brown to black, and falls off on its own. What’s left underneath is the belly button.
The final shape depends on how the skin, scar tissue, and underlying muscle close up during this healing process. If the tissue forms a flat or concave scar, you get an innie. If extra scar tissue develops or the skin heals in a way that pushes outward, you get an outie. This process is largely random and unique to each individual, which is why siblings raised in identical conditions can end up with different belly button shapes.
Where Genetics Plays a Small Role
While there’s no “outie gene,” genetics does influence one important factor: how well the umbilical ring closes after birth. The umbilical ring is the gap in the abdominal wall muscles where the cord passed through. In most babies, this ring seals shut completely within the first year or two of life. But in some, it doesn’t close all the way, which can lead to an umbilical hernia, a condition where tissue pushes through the gap and creates a visible bulge at the belly button.
Umbilical hernias are common. Roughly 15 to 23 percent of all newborns in the United States have one, though the rate drops to 2 to 10 percent by age one as the ring closes naturally. Research in animal genetics has found that the tendency toward incomplete umbilical ring closure has a moderate heritability of about 0.25, meaning genetics accounts for roughly a quarter of the variation. Several specific genes involved in tissue development and cell differentiation have been linked to this trait, though research in humans is less definitive.
So if your outie is caused by an umbilical hernia (which is the case for many outies), there may be a genetic predisposition at play. But the hernia itself, not a gene for belly button shape, is the heritable part.
Umbilical Hernias and Outie Appearance
An umbilical hernia happens when the abdominal muscles don’t fully join together at the midline after birth, allowing a small portion of intestine or fatty tissue to push through. In infants, this is especially visible when the baby cries or strains, causing the belly button to protrude. This is one of the most common reasons a baby develops what looks like an outie.
Most childhood umbilical hernias resolve on their own within the first two years, though some persist into age five or beyond. Once the hernia closes, the belly button may flatten into an innie, or it may retain some outward shape depending on how the tissue healed. Premature babies and those with low birth weights are at significantly higher risk. The incidence can be as high as 84 percent in newborns weighing between 1,000 and 1,500 grams, compared to about 20 percent in babies weighing 2,000 to 2,500 grams. Black infants in the United States also have higher rates, with reported incidence as high as 26.6 percent, though the reasons for this difference aren’t fully understood.
Other Factors That Shape the Belly Button
Beyond hernias, a few other things can influence whether a belly button protrudes. An umbilical granuloma, a small nodule of tissue up to 1 centimeter across, can form after the cord stump separates. This extra growth of tissue at the base of the belly button can create a bumpy or protruding appearance. Granulomas are typically treated easily and aren’t genetic.
Body composition also matters over time. Weight gain, pregnancy, and changes in abdominal muscle tone can all alter the appearance of a belly button. Some people with innies develop a more protruding look during pregnancy as the abdominal wall stretches, then return to their original shape afterward. Others find that significant weight changes permanently alter their navel’s appearance.
The Cord Clamping Myth
One persistent belief is that the way a doctor or midwife clamps or cuts the umbilical cord determines whether you get an innie or outie. This isn’t true. The clamp is placed on the cord itself, well above the skin surface, and the stump that remains dries up and falls off regardless of technique. The healing process underneath is driven by the baby’s own tissue, not by anything the medical team does during delivery. There is no clinical evidence that clamping method, cord length, or cutting technique affects belly button shape.
Can an Outie Be Changed?
If an outie bothers you cosmetically, a procedure called umbilicoplasty can reshape the belly button. The surgery anchors the belly button tissue to the deep abdominal wall and reshapes the skin to create a more concave appearance. It’s also commonly performed as part of a tummy tuck. The typical belly button measures 1.5 to 2 centimeters across, and surgeons aim to recreate a natural-looking round or oval depression.
Complications are uncommon but can include scarring, skin discoloration, or a result that looks flat rather than deeply recessed. For children with umbilical hernias that haven’t closed by age five, surgical repair of the hernia itself often resolves the outie appearance as a side effect.