pediatrics
Neonatal Hyperbilirubinemia
Introduction
Jaundice is a yellow discoloration of the skin and eyes caused by hyperbilirubinemia (elevated serum bilirubin concentration). The serum bilirubin level required to cause jaundice varies with skin tone and body region, but jaundice usually becomes visible on the sclera at a level of 2 to 3 mg/dL (34 to 51 micromol/L) and on the face at about 4 to 5 mg/dL (68 to 86 micromol/L). With increasing bilirubin levels, jaundice seems to advance in a head-to-foot direction, appearing at the umbilicus at about 15 mg/dL (257 micromol/L) and at the feet at about 20 mg/dL (342 micromol/L). Slightly more than half of all neonates become visibly jaundiced in the first week of life. Almost all hyperbilirubinemia in the immediate neonatal period is unconjugated, which is termed indirect bilirubin, based on older laboratory measurement methods; conjugated bilirubin is termed direct bilirubin. For further discussions of cholestasis and disorders of bilirubin excretion in the neonatal period see Neonatal Cholestasis . 