I've heard some mothers complain that their baby's navel is big. This condition is called an umbilical hernia and 10% of babies have it. Normally, after the umbilical cord is cut, the stump withers or fall off, after which the umbilical ring closes. But if the umbilical ring remains open, the child has an umbilical hernia (big navel).
The belly button will look like a balloon and can be pushed back into the belly, although it will come back out again. Umbilical hernia is not a cause for alarm. In the past, the treatment for umbilical hernias was to push in the belly button, tape a coin over the belly to prevent it from coming out again. By the time the baby is a year old, the umbilical hernia would have disappeared but there's the risk of skin irritation.
But if you decide to leave the umbilical hernia alone, it works too, because by age 1 the hernia is likely to disappear by itself. Although the smaller the hernia (not the balloon o), the quicker the hernia is to close by itself. Even the biggest hernia should close by age 5 although the ones that appear after 6 months of age are less likely to disappear.
If you're really concerned, you can have surgery performed on your child. If after one year, the ring is still bigger than 2cm the only time you should be worried about umbilical hernias is if it becomes incarcerated (when you can't push the belly button back into the child's abdomen when he's relaxed) if that's not the case then there's no cause for alarm.
The surgery is perfectly simple and safe. The incision is tiny, and a couple of stitches usually suffice to close the remaining hole in the linea alba. And before you say Jack Robinson, your child's navel is flat!