Doctors use the navel as a reference point on the belly, for example when examining a patient. Most of us just call it the belly button. Whatever the name, it is a scar, the first one you ever got. It is left over from the umbilical cord, and it marks the spot where that cord was attached before you were born.

Before birth, a baby does not breathe air, so the placenta does the work of the lungs. Oxygen comes in through the cord. Blood rich in oxygen and nutrients flows from the placenta to the baby so the baby can grow. The cord has three blood vessels, one vein and two arteries. The two arteries carry oxygen-poor blood from the baby back to the placenta.

The cord is long and thin. At full term it is about 55 to 60 centimeters long, around 22 inches, and about 1 to 2 centimeters thick. The vessels are held in a soft, jelly-like cushion called Wharton's jelly.

After birth the baby breathes air with its lungs, and the cord is cut. Doctors often wait a short time before doing it. As of November 2026, the American group of doctors called ACOG advises waiting at least 30 to 60 seconds for healthy babies. Waiting lets extra blood move from the placenta to a full-term baby. This gives the baby more iron stored in the body in the first months of life.

The cut leaves a short stump on the baby's belly. The stump changes color as it dries. At first it is soft, moist and bluish white or yellowish green. Then it turns yellow, then brown or black before it falls off. This usually takes one to three weeks. A stump that has not fallen off by about 3 weeks needs a doctor's look.

The care is simple. Keep the stump clean and dry. Leave it alone, and do not pull or tug at it. There is no need for alcohol, lotion or anything else on it, and plain water is enough if it gets dirty. A stump heals much like a scab: it dries, shrinks and falls off, and the belly button shows underneath. Inside, the opening of the cord heals and seals itself shut.

What the skin looks like afterward is mostly chance. Most belly buttons are innies, and outies are fewer. Whether you have an innie or an outie may depend on how the skin heals after the stump falls off. How a doctor cut or tied the cord does not decide it, and nobody gets to choose.

Sometimes an outie has a cause. Some outies are caused by an umbilical hernia or an umbilical granuloma. Both are generally harmless, but a doctor should look at them. A granuloma is a small, moist, pink or red lump of extra scar tissue. It is usually harmless and often goes away in about a week.

An umbilical hernia forms when part of the intestine pushes through a weak spot in the belly muscles near the belly button. A child's hernia usually needs treatment only if it is very big or does not go away. One larger than about 2 centimeters is more likely to need surgery. Most go away on their own by about age 5.

The belly button is also a home for living things. A study of 60 belly buttons found 2,368 kinds of bacteria. On average, each belly button in the study had about 67 kinds, though some had as few as 29 and some as many as 107. A scar that began as a lifeline now carries a small world of its own.

Words to know

• navel: belly button
• placenta: acts as lungs
• granuloma: small lump
• hernia: a bulge
• bacteria: tiny living things