What is Neonatal Bilirubin?

Neonatal bilirubin refers to the levels of a bodily substance called bilirubin in newborns. Bilirubin is produced by a process of the liver whereby certain red blood cells are broken down. In infants, insufficient liver function often results in high blood levels of bilirubin. High levels of neonatal bilirubin lead to a condition called neonatal jaundice, or neonatal hyperbilirubinemia. Left untreated, jaundice can be dangerous, causing sluggish behavior and eating habits, and potentially leading to brain damage and even death.

Bilirubin is a pigment naturally found in bile that is reddish-yellow. In healthy newborns and adults, it is broken down by the liver and passed out in fecal matter. There are two types of bilirubin: indirect, or unconjugated; and direct, or conjugated. Both types are found in the blood stream, but direct bilirubin is soluble and easily passes out of the body while indirect bilirubin is insoluble and remains in the blood stream until broken down.

It is a newborn's inability to break down levels of indirect bilirubin that causes jaundice. Sometimes, the inability for an infant to break down bilirubin is an indicator of serious liver problems. Most often, however, an infant merely needs time and perhaps a little help for liver function to get up to full speed.

Neonatal bilirubin is usually nothing to be scared about. In fact, jaundice occurs in the majority of newborns, as it can take some time for infants to adapt to the job of doing their own liver processing. In some infants, however, persistently high levels of neonatal bilirubin can indicate a faulty liver, a life-threatening condition that requires serious and swift medical action.

Persistent jaundice in infants doesn't necessarily indicate liver damage, however. It may just be that the infant needs a little help to get all systems going. For such a purpose, most hospitals are equipped with phototherapy fluorescent lights—like infant tanning beds—that serve to break down bilirubin. These lights are often referred to as bili lights. Hospitals also have fiber-optic blankets, equipped with bili lights, that parents may take home for further treatment.

Hospitals take neonatal bilirubin very seriously, so much so that tests for bilirubin are at the top of the list after birth. Within 24 hours of birth, infants should have skin and blood tests conducted to check bilirubin levels. If levels are too high, doctors may check for problems with the liver or obstructions blocking bile ducts. If none of those issues are a factor, yet jaundice persists, an infant will likely be put under bili lights until symptoms of jaundice subside.