Belly buttons may be cute – and some are even bling-worthy – but they don't serve much of a purpose. That's a good thing, considering the many people who are living happy, navel-less lives.

How can this happen?

The culprits are two types of hernias, or holes, that can be present in the abdominal wall at birth: gastroschisis and omphalocele.

"My son has no belly button," says mom Becki Noles. "Instead, he has a slight indentation." Noles' son was born with gastroschisis.

Babies with this condition have a hole in their abdominal wall on one side of the umbilical cord. At birth, the intestines protrude through this hole. Noles' son's gastroschisis was fully corrected with surgery, but the belly button itself was a goner.

"Most parents of babies with gastroschisis don't even see the belly button, but it's there," says Faisal Qureshi, a pediatric surgeon at Children's National Medical Center in Washington, D.C. Surgeons put the intestine back into the abdomen and sometimes can stretch the belly button over the hole. "When we do it this way, the belly button itself forms the barrier," says Qureshi.

But in other cases – such as with Noles' son – the hole is too big to do that. "If we aren't able to save the cord, we often will try to cinch the closure the way you would a purse string, which pulls it into a circular shape," says Shaheen Timmapuri, a pediatric surgeon at St. Christopher's Hospital for Children in Philadelphia. "It's sort of crinkly and creates the appearance of a belly button."

Babies who have an omphalocele, on the other hand, truly are born without a belly button. The intestines or other abdominal organs protrude through a hole in the middle of the baby's abdomen, right where the belly button would be.

Here's how it happens:

Early in pregnancy, the umbilical cord is attached to the baby internally, not externally. Around the 11th week, the abdominal wall should seal off the intestines, leaving just a small hole for the umbilical cord. Later, the abdominal muscles should grow together, sealing it off entirely and creating what we call the belly button.

An omphalocele occurs when this process doesn't happen the way it's supposed to. In contrast with gastroschisis, abdominal organs may protrude in addition to the intestines, and whatever protrudes is encased in a lining.

"Imagine a piece of cloth with a big hole in it," Qureshi says, "and then imagine putting a sock through the hole. That sock is the lining, and the intestines [and other organs] are inside the sock."

Doctors repair the omphalecele surgically or, in some cases, using a technique called "painting," in which the lining is dried off with betadyne or a similar material, allowing the skin to grow over it. This is usually followed up with surgery to repair the muscle when the child is a little older.

"Babies with omphaloceles definitely do not have belly buttons, so generally we try to fashion something to give the appearance of one," says Timmapuri.

It can be scary and unsettling if your baby has one of these conditions. Fortunately, excellent treatments are available. In some cases, all that remains of the difficult experience is a tiny scar.

According to the U.S. National Institutes of health, how well a child does depends on whether he has other conditions that go with it, and if so, which ones. Related birth defects are rare in babies with gastroschisis, but an estimated 25 to 40 percent of infants with an omphalocele have other birth defects, such as chromosomal abnormalities and heart defects.

If your baby has one of these abdominal wall defects, you can find support and more information from other parents in the BabyCenter Community. Visit our gastroschisis and birth defects groups, or search the Community for "omphalocele" to find related discussions.