Relationship of serum bilirubin levels to ototoxicity and deafness in high-risk low-birth-weight infants.

During a 4-year period, 12 premature infants, all less than 34 weeks of gestation and all with a bilirubin level above 240 mumol/L (14 mg/dL) were determined to have bilateral sensorineural deafness. In order to to investigate how far the hyperbilirubinemia or any a associated factor might have been a causative factor, all infants of 34 weeks of gestation or less who had a serum bilirubin level above 240 mumol/L were investigated. For a period of 4 years, 99 infants meeting these criteria were classified as high risk or low risk on the basis of perinatal risk factors. Eight of the 22 high-risk infants with birth weight less than 1,500 g, but only two of 43 high-risk infants with birth weight greater than 1,500 g were deaf (P less than .05). The deaf infants were also matched with infants of normal hearing who had similar bilirubin levels and the same number of adverse perinatal factors. The mean duration of hyperbilirubinemia was significantly longer in the deaf infants (P less than .02), and they appeared to have a greater number of acidotic episodes while they were hyperbilirubinemic. These findings suggest that in healthy preterm infants with birth weight greater than 1,500 g, high bilirubin levels carry little risk, whereas a serum bilirubin level greater than 240 mumol/L in high-risk preterm infants with birth weight of 1,500 g or less is associated with a high risk of deafness.