• newborns have increased rates of bilirubin production due to RBC's with shorter life spans, and a decreased rate of bilirubin elimination due to decreased ability of the neonatal liver to conjugate bilirubin
• about 60% of newborns will become clinically jaundiced
• bilirubin levels peat at 4 days of life,  and may not decline before day 7
• admission and treatment should be considered urgently when serum total bilirubin >25mg/dL, with exchange transfusion if it is >30mg/dL or the infant has signs of kernicterus
• there are nomograms which plot the bilirubin level according to the infant's age in hours to determine if an infant is at risk for being at toxic levels
• the most common pathologic etiologies are due to increased bilirubin production: blood-group incompatibilities, RBC-enzyme deficiency, and RBC structural defects
• when jaundice occurs between days 4-7, strongly consider sepsis, UTI, congenital infection (syphilis, CMV, etc)

References