Physiologic jaundice of the newborn, the most common cause of newborn jaundice, is present to some degree in almost all newborns. At birth, babies have relatively immature liver function.

Therefore, even the normal destruction of red blood cells by the liver in the newborn infant can cause jaundice. This form of jaundice usually appears between the 2nd and 5th days of life and clears by 2 weeks. It usually causes no problems.

Breast-feeding jaundice is seen in 5-10% of newborns. It is similar to physiologic jaundice, but bilirubin levels tend to be slightly higher. This occurs when breast-fed babies do not take in enough breast milk and rarely requires treatment.

Sometimes, however, breast-feeding does need to be interrupted and bottle-feeding substituted for a brief period of time to clear the jaundice.

Jaundice in a newborn is rarely caused by a serious illness. Disorders which can cause jaundice in a baby include:

• biliary atresia
• ABO incompatibility (similar to a transfusion reaction, caused when fetal and maternal blood mingle before birth)
• Rh incompatibility (Anti-Rh antibodies)
• galactosemia (see galactosemia screen)
• cephalohematoma
• polycythemia
• glucose-6-phosphate dehydrogenase deficiency
• neonatal sepsis
• congenital cytomegalovirus infection (CMV)
• congenital toxoplasmosis
• congenital syphilis
• congenital herpes
• congenital rubella
• late pregnancy administration of sulfa drugs to the mother
• Crigler-Najjar syndrome
• spherocytosis (congenital hemolytic anemia)
• cystic fibrosis
• pyruvate kinase deficiency
• thalassemia
• Gilbert's syndrome
• congenital hypothyroidism
• Lucey-Driscol syndrome
• Gaucher's disease
• Niemann-Pick disease