When pressing on a baby's umbilical hernia, a sound may be heard, primarily because the contents of the hernia are the intestines, most commonly the small intestine. Digestive fluids and gases are present in the intestines, so when pressed, the movement of gas through the digestive fluid can easily produce a sound, which is normal.

The occurrence of an umbilical hernia in babies is mainly due to the incomplete development of the abdominal wall muscles and the umbilical ring not being fully closed. This allows internal organs like the intestines and mesentery to protrude through the umbilical ring, leading to symptoms of an umbilical hernia. After the appearance of an umbilical hernia, most children's hernias close on their own within the first year, with only a minority requiring surgical treatment.