What causes hyperbilirubinemia in newborn?

Hyperbilirubinemia in newborns is primarily caused by an immature liver that is unable to effectively process and excrete bilirubin, a byproduct of red blood cell breakdown. Conditions such as hemolytic disease (e.g., Rh or ABO incompatibility), bruising from birth trauma, or certain metabolic disorders can increase bilirubin production. Additionally, factors like breastfeeding jaundice or delayed meconium passage can contribute to elevated bilirubin levels. Most cases resolve with time or simple treatments, but severe cases may require phototherapy or other interventions.