PHYSIOLOGIC JAUNDICE
Physiologic jaundice in healthy term newborns follows a typical pattern. The average total serum bilirubin level usually peaks at 5 to 6 mg per dL (86 to 103 μ mol per L) on the third to fourth day of life and then declines over the first week after birth.2 Bilirubin elevations of up to 12 mg per dL, with less than 2 mg per dL (34 μ mol per L) of the conjugated form, can sometimes occur. Infants with multiple risk factors may develop an exaggerated form of physiologic jaundice in which the total serum bilirubin level may rise as high as 17 mg per dL (291 μ mol per L).3
Factors that contribute to the development of physiologic hyperbilirubinemia in the neonate include an increased bilirubin load because of relative polycythemia, a shortened erythrocyte life span (80 days compared with the adult 120 days), immature hepatic uptake and conjugation processes, and increased enterohepatic circulation.7