Research Highlights

Risk factors for bilirubin encephalopathy defined

Published online 19 October 2011

Mohammed Yahia

Urijamjari / Flickr

Neonates born with a high level of bilirubin, a breakdown product of red blood cells, in their blood need phototherapy, or exchange transfusions in severe cases, to protect them from bilirubin encephalopathy — a neurological condition that can lead to brain damage.

Rasha Gamaleldin, a pediatrician from Cairo University, led a team of researchers from Cairo University and University of Washington in Seattle to study the tolerance level of blood bilirubin. The study enrolled 249 newborns admitted to Cairo University Children's Hospital with a concentration of total serum bilirubin (TSB) ranging from 25–76.4 mg/dL. The study's findings are published in the journal Pediatrics.

The researchers found that children with no neurotoxicity risk factors, including: prematurity, anemia, significant lethargy, sepsis, acidosis, asphyxia, temperature instability, amongst others, could tolerate bilirubin levels higher than the standard of 25 mg/dL. In 111 infants with risk factors, the threshold for acute bilirubin encephalopathy was 31.5 mg/dL.

However, infants with Rh hemolytic disease, in which antibodies from the mother pass through the placenta and attack the child's red blood cells, had a significantly higher risk for bilirubin encephalopathy. ABO incompatibility, another risk factor that occurs when non-compatible blood types are mixed, had a lesser effect on the increased risk for bilirubin encephalopathy.

The study's authors contend that the risk of developing bilirubin encephalopathy from haemolytic diseases depends on the etiology of the disease. They suggest there may be other biological factors that are as yet unknown which may be altered by the neurotoxicity risk factors.


  1. Gamaleldin, R. et al. Risk Factors for Neurotoxicity in Newborns With Severe Neonatal Hyperbilirubinemia. Pediatric (September 2011)  doi: 10.1542/peds.2011-0206