If your baby has a prominent outie, it could be hiding an umbilical hernia, a defect or hole in the abdominal wall beneath the belly button, says Donna Caniano, M.D., chief of pediatric surgery at Columbus Children's Hospital in Ohio. You can see the difference between a hernia and a simple outie belly button when your baby cries: A hernia will puff out even further like a balloon when it's strained. Umbilical hernias occur in about 10 percent of infants, but the majority don't require any treatment. Most of these hernias are less than an inch in diameter, and will close up on their own in the first two years of life, notes Dr. Caniano. Rarely, a larger umbilical hernia may eventually require surgery, especially on girls, who could face complications from it during pregnancy. Meanwhile, you can try to coax a hernia to close by dressing your baby in diapers that come up high over her belly button and fastening them tightly. Don't tape a coin over the navel, a traditional trick. The metal in the coin can irritate your baby's skin.