Excess bilirubin (hyperbilirubinemia) is the main cause of jaundice. Bilirubin, which is responsible for the yellow color of jaundice, is a normal part of the pigment released from the breakdown of "used" red blood cells.
Newborns produce more bilirubin than adults do because of greater production and faster breakdown of red blood cells in the first few days of life. Normally, the liver filters bilirubin from the bloodstream and releases it into the intestinal tract. A newborn's immature liver often can't remove bilirubin quickly enough, causing an excess of bilirubin. Jaundice due to these normal newborn conditions is called physiologic jaundice, and it typically appears on the second or third day of life.
An underlying disorder may cause infant jaundice. In these cases, jaundice often appears much earlier or much later than does the more common form of infant jaundice. Diseases or conditions that can cause jaundice include:
- Internal bleeding (hemorrhage)
- An infection in your baby's blood (sepsis)
- Other viral or bacterial infections
- An incompatibility between the mother's blood and the baby's blood
- A liver malfunction
- Biliary atresia, a condition in which the baby's bile ducts are blocked or scarred
- An enzyme deficiency
- An abnormality of your baby's red blood cells that causes them to break down rapidly