Episode Details

Episode 133: Neonatal Jaundice

Jennifer explained the pathophysiology of neonatal jaundice and how to treat it and described why screening for hyperbilirubinemia is important.    

Written by Jennifer Lai, MS3, College of Osteopathic Medicine of the Pacific Western University of Health Sciences. Comments by Hector Arreaza, MD.  

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What is neonatal jaundice? 

Jenni: Infant jaundice, also known as hyperbilirubinemia, is when there is a high level of serum bilirubin causing yellow discoloration of the newborn's skin and eyes. Bilirubin is a red-orange byproduct of hemoglobin catabolism that gives yellow pigment to skin and mucosa membranes. 

Arreaza: When we see jaundice on the eyes, it is actually the conjunctiva color we are seeing. So, the term “scleral icterus” should be changed to “conjunctival icterus,” but you may get corrected by unaware clinicians. Bilirubin actually binds elastin.

What’s the pathophysiology/ big picture?

Jenni: The key problem is the accumulation of high levels of bilirubin in serum and if left untreated, it can bind to tissues and cause toxicity. There are multiple reasons why there might be too much bilirubin in the serum. Excess bilirubin can be due to a benign normal condition, but it can also be due to a pathologic reason. It is important to differentiate between these two because the management and treatment can differ significantly. 

Arreaza: Highly bilirubin means that it is being either overproduced or under-eliminated. 

Physiologic jaundice 

Most of the time, hyperbilirubinemia is benign and physiologic, with yellowing typically occurring between 2-4 days. 

Normally, there is a period of transition caused by the turnover of the fetal red blood cells and the immaturity of the newborn’s liver to efficiently metabolize bilirubin and increased enterohepatic circulation. The most common reason is that the liver isn't mature enough to get rid of the bilirubin in the bloodstream or because the baby’s gut is sterile, so it does not have the bacteria to convert the bilirubin to get it out of the body. In general, newborns have a higher level of total serum or plasma bilirubin levels compared to adults for the following reasons: 

• Newborns have more red blood cells (hematocrit between 50-60), and fetal red blood cells have a shorter life span (85 days vs. 120 days) than those of adults. After birth, there is an increased turnover of fetal red blood cells, so there is more bilirubin.
• Bilirubin clearance (conjugation and excretion) is decreased in newborns, mainly because of a deficiency of the hepatic enzyme UGT.
• Increase in the enterohepatic circulation of bilirubin as the amount of unconjugated bilirubin increases due to the limited bacterial conversion of conjugated bilirubin to urobilin.

Pathologic Jaundice

Pathologic jaundice includes severe neonatal hyperbilirubinemia, extreme neonatal hyperbilirubinemia, and bilirubin-induced neurologic disorders. We determine the severity of the jaundice using the total serum bilirubin (TSB). It is defined as a TSB >25 (severe) and TSB >30 (extreme). Other concerning signs include a TSB over the 95% percentile, a greater than 5mg/dL/day or 0.2mg/dL/hour, or jaundice that lasts for more than 2-3 weeks. 

Potential pathologic causes include but are not limited to: 

1. Increased bilirubin production from increased hemolysis which is when the re