Each year approximately 60% of the 4 million newborns in the United States become clinically jaundiced. Many receive various forms of evaluation and treatment. Few issues in neonatal medicine have generated such long-standing controversy as the possible adverse consequences of neonatal jaundice and when to begin treatment. Questions regarding potentially detrimental neurologic effects from elevated serum bilirubin levels prompt continuing concern and debate, particularly with regard to the management of the otherwise healthy term newborn without risk factors for hemolysis. Although most data are based on infants with birth weights ≥2500 g, "term" is hereafter defined as 37 completed weeks of gestation.
Under certain circumstances, bilirubin may be toxic to the central nervous system and may cause neurologic impairment even in healthy term newborns. Most studies, however, have failed to substantiate significant associations between a specific level of total serum bilirubin (TSB) during nonhemolytic hyperbilirubinemia in term newborns and subsequent IQ or serious neurologic abnormality (including hearing impairment). Other studies have detected subtle differences in outcomes associated with TSB levels, particularly when used in conjunction with albumin binding tests and/or duration of exposure. In almost all published studies, the TSB concentration has been used as a predictor variable for outcome determinations.
Factors influencing bilirubin toxicity to the brain cells of newborn infants are complex and incompletely understood; they include those that affect the serum albumin concentration and those that affect the binding of bilirubin to albumin, the penetration of bilirubin into the brain, and the vulnerability of brain cells to the toxic effects of bilirubin.