Bilirubin is a yellow breakdown product of normal heme catabolism. Its levels are elevated in certain diseases and responsible for the yellow color of bruises.

Risk to Newborns

Hyperbilirubinemia is one of the most common problems encountered in term newborns. Up to 60% of term newborns have clinical jaundice in the first week of life. Excessive bilirubin damages developing brain cells in infants (kernicterus) and may cause mental retardation, learning and developmental disabilities, hearing loss, or eye movement problems. It is important that bilirubin levels in newborns not get too high. When the level of bilirubin is above a critical threshold, special treatments are initiated to lower it.

High Bilirubin Levels are Common in Newborns

High bilirubin levels in newborns are relatively common, especially within three days of birth. This is sometimes called physiologic jaundice of the newborn. Within the first 24 hours of life, up to 50% of full-term newborns, and an even greater percentage of pre-term babies, may have a high bilirubin level. After birth, newborns begin breaking down the excess red blood cells (RBCs) they are born with and, since the newborn’s liver is not fully mature, it is unable to process the extra bilirubin, causing levels to rise in the blood and other body tissues. This situation usually resolves itself within a few days.