Newborn jaundice —yellowing of the skin and the sclera of the eye—occurs in up to 60% of full-term infants. The discoloration occurs when levels of total serum bilirubin exceed 4 milligrams per deciliter (mg/dL [68.4 µmol/L]). Bilirubin is a breakdown product of blood cells. In most cases, jaundice is short-lived and harmless, and may resolve without treatment. When necessary, treatment involves phototherapy, use of a special light to break down bilirubin in the baby’s skin, or a special type of blood transfusion.

In rare cases, bilirubin reaches dangerous levels—greater than 30 mg/dL (513 µmo/L)—which can lead to a form of brain damage called kernicterus. While it is known that small increases in bilirubin are benign and severe increases are dangerous, the health effects of moderately elevated levels, those from 25-30 mg/dL (427-513 µmol/L), are unclear.

Researchers compared brain function at ages 2 and 5 between children who had moderately elevated and normal bilirubin levels shortly after birth. Their findings, in the May 4, 2006 issue of the New England Journal of Medicine , show that children with bilirubin levels between 25-30 mg/dL (427-513 µmol/L) scored the same on measures of cognitive and neurologic function as children with normal bilirubin levels during infancy.

About the Study

Researchers from the University of California, San Francisco and Kaiser Permanente Medical Care Program studied 140 infants with bilirubin levels of 25 mg/dL (427 µmol/L) or greater and 419 infants with lower levels (called “controls”). The children with jaundice were treated with either phototherapy or exchange transfusion. About 90% of the children were evaluated at age two; at age five, 59% of the high bilirubin group and 40% of the controls were evaluated again.

Cognitive and neurologic function--including IQ, motor skills, and behavior--were assessed through tests, questionnaires, and medical chart reviews. The results of these assessments were compared between the two groups of children.

There were no differences in cognitive and neurologic function between the two groups. There were also no cases of kernicterus. Lower IQ scores were seen, however, in a small subgroup (nine children) of the high bilirubin infants who also had a positive direct Coombs test. This test result indicates a possible blood disorder.

The bilirubin levels in this study ranged from 25-30 mg/dL (427-513 µmol/L), with the majority of levels closer to 25. Therefore, these findings do not apply to children with levels greater than 30 mg/dL (513 µmol/L).

How Does This Affect You?

These findings provide reassurance to parents and expectant parents that when detected quickly and treated appropriately, total serum bilirubin levels in the range of 25-30 mg/dL (427-513 µmol/L) do not have adverse effects on IQ, motor skills, and behavior in infants born at or near term. In an accompanying editorial, Dr. Jon Watchko calls for continued vigilance in screening infants for elevated bilirubin both before and after hospital discharge, and beginning treatment quickly when appropriate.

This study also highlights the possible adverse effects of a positive direct Coombs test on IQ, and the importance of detecting this abnormal test result. Talk with your doctor about the newborn screening done at your hospital to ensure the appropriate tests are done for your child.