An innie is a belly button that curves inward, creating a small hollow or depression in the center of your abdomen. About 90% of people have one. The remaining 10% have an outie, where the navel protrudes outward instead. Both are completely normal variations of the scar left behind after your umbilical cord detaches.
How an Innie Forms
Your belly button is not shaped by the doctor or midwife who delivered you. When the umbilical cord is cut at birth, a small stump is left attached to the baby’s abdomen. Over the next one to three weeks, that stump dries out and falls off on its own. What remains is a scar, and the shape it takes depends on what happens underneath the skin as the wound heals.
During healing, four internal structures that once connected to the cord (a vein, two arteries, and a tube leading to the bladder) close off and retract deeper into the body. As they pull inward, the overlying skin follows, creating the concave shape of an innie. Whether you end up with an innie or outie comes down to how much scar tissue forms during this process and how the skin attaches to the underlying muscle wall. The way the cord is cut or clamped has no influence on the outcome.
Innies vs. Outies
The distinction is straightforward: any concave navel is an innie, and any convex navel is an outie. Outies form when the tip of the cord’s remnant protrudes past the surrounding skin rather than retracting inward. This is a cosmetic variation, not a medical problem.
That said, not every protruding belly button is simply an outie. An umbilical hernia can create a soft bulge on or near the navel that looks similar. Hernias happen when a small section of intestine, fat, or fluid pushes through a weak spot in the abdominal wall muscle. In adults, the bulge might only appear when you lift something heavy or strain your core. In babies, it sometimes shows up only during crying. A hernia feels soft to the touch and can often be gently pushed back in. If your belly button has changed shape or a new bulge has appeared, a simple physical exam can determine whether it’s a hernia.
Why Innies Change During Pregnancy
If you’ve always had an innie, pregnancy can temporarily flip it. As the uterus expands, it puts increasing pressure on the abdominal wall from inside, physically pushing the navel outward. This is harmless and extremely common. After delivery, the belly button typically returns to its original innie shape as the abdomen gradually recovers.
Cleaning a Deep Innie
The fold of an innie belly button is a warm, sheltered spot that naturally collects dead skin cells, oil, sweat, lint, and bacteria. Research from the Belly Button Biodiversity Project found a median of 67 distinct bacterial species living in a single navel. Most of these are harmless, but poor hygiene in a deep navel can lead to odor, irritation, or infection over time.
In rare cases, a buildup of skin oils and dead cells can harden into a dark, stone-like mass called an omphalolith, or navel stone. These are most common in people with deep, narrow belly buttons, and risk factors include older age and obesity. Navel stones get their dark color from a combination of pigment accumulation and oxidation. If one forms, it can be softened with a drop of olive oil or glycerin and gently removed.
For everyday cleaning, a damp cotton swab or washcloth run gently through the folds of your navel during a shower is enough. If your belly button tends to stay moist, drying it thoroughly afterward helps prevent fungal growth. People with deeper innies simply need to be a bit more deliberate about it than those with shallow ones.
Changing Your Belly Button Shape
A procedure called umbilicoplasty can reshape the navel, converting an outie to an innie or refining the appearance of an existing innie. It’s a relatively minor outpatient surgery that adjusts the scar tissue and reattaches the skin to the abdominal wall to create a natural-looking depression. Some people pursue it purely for cosmetic reasons, while others have it done alongside hernia repair or a tummy tuck, where the navel needs to be repositioned after excess skin is removed. Recovery is typically quick, with most people returning to normal activity within a few weeks.