The neurodevlopmental risks associated with neonatal total serum bilirubin levels of 25 mg/dL or higher in 140 affected infants were compared with 419 randomly selected controls from a cohort of term-infants born 1995-1998 in Kaiser Permanente hospitals in northern California. Peak bilirubin levels were between 25 and 29.9 mg/dL in 130 newborns with hyperbilirubinemia and 30 mg/dL or higher in 10 newborns. Phototherapy was used in 136 cases and exchange transfusion in 5. There were no cases of kernicterus. In subjects followed for at least 2 years, scores on cognition tests were similar in the hyperbilirubinemia and control groups. Questionable or abnormal neurologic findings were present in 14 children (17%) with hyperbilirubinemia vs 48 of controls (29%); P=0.05. Reported behavioral problems were not significantly different in the 2 groups. Those with positive direct antiglobulin tests for immune-mediated hemolytic disease in the hyperbilirubinemia group had lower scores on cognition tests but not more neurologic or behavioral problems. 
COMMENT. When treated with phototherapy or exchange transfusion, neonates born at or near term and having a total serum bilirubin of 25-30 mg/dL for less than 6 hours showed no increase in neurodevelopmental or behavioral problems at follow-up compared to controls. In an editorial, Watchko JF  points out that factors other than serum bilirubin level and coexisting hemolysis can increase the risk of kernicterus: reduced albumin binding of bilirubin, low gestational age, glucose-6-phosphate dehydrogenase deficiency, and acidosis. These factors may lower the serum bilirubin level at which treatment is indicated. In 116 reported cases of kernicterus, 90 had total serum bilirubin levels of 30 mg/dL or more and 76 had levels of 35 mg/dL or more.