Introduction

Jaundice (Jon - dis) is very common in the newborn period.  In our experience, about  30-40% of newborns have some degree of jaundice by the time they are discharged home from the nursery.  Simply put, jaundice is an abnormal yellow coloring of the skin.  Because jaundice is a symptom of a very broad set of clinical conditions, we will only discuss the common jaundice in the newborn period - also called physiologic jaundice.  In most cases, an other wise healthy term newborn with no risk factors will not require any special treatment other than observation.  In those that do require treatment, the vast majority will not require anything more than treatment with a special light commonly called “bili-lights” and, sometimes, IV fluids.

What Causes Jaundice?

A natural component of blood cells is a chemical substance called bilirubin (Billy - roob - en).  In a constant life cycle of blood cells in your body, old red blood cells are destroyed as new ones are made.  It is during the destruction of red blood cells that bilirubin is released into the blood.  When accumulated in large quantities, the bilirubin becomes visible as a yellow pigment in the blood.

When the bilirubin is released it is processed in two ways.  The liver recycles some of it to make more blood cells but also dumps some of it into the intestines giving the yellow & brown color to stool.  In the skin, specific wavelengths of light convert the bilirubin into a form that is then passed out of the body by the kidneys in urine.   So the bilirubin is eliminated from the body in both stool and urine.

Any abnormal elevation in bilirubin is called “hyperbilirubinemia” (hyper - billy - roob - in - ee - mia).  Therefore, jaundice is a visible sign of hyperbilirubinemia.  You may hear the terms interchanged, but they are not completely interchangeable.

In the newborn infant, there are multiple factors that may cause the bilirubin to rise to visible levels causing jaundice.  First, newborns are often born with more blood than they need.  So, as the blood breaks down, there is a large quantity of bilirubin released.  Second, the newborn liver may not be quite mature enough to process the bilirubin efficiently.  Third, it is natural for newborns to lose weight during the first few days until the mother’s milk supply comes in.  Because clearance of bilirubin depends on stool and urine, the bilirubin accumulate more quickly than it can be cleared.  The combination of these factors in the newborn period is called “physiologic jaundice”.  You may also hear the term “breastmilk jaundice”, but that is a separate condition that presents after the immediate newborn period.

Blood type incompatibility is a common cause of increased blood cell destruction in the newborn period.  If the mother and baby have different blood types, then the mother’s immune system may make antibodies against the baby’s blood.  This is usually not a problem during the pregnancy, but during the birthing process some of those antibodies may spill into the baby’s circulation.  When this happens, the antibodies will attack and destroy the baby’s red blood cells thus causing increased red blood cell destruction and subsequent jaundice.  Luckily, there is only a limited amount of antibodies and when they are all used up the jaundice subsides.

Finally, there is a very long list of illnesses that can cause jaundice.  In the newborn period, serious infections including sepsis and urinary tract infections can cause jaundice.  These are uncommon in an otherwise term newborn with no risk factors.  Causes even less common than infections include things like hypothyroidism, biliary atresia, and inherited disorders.  These are beyond the scope of this discussion, but things we always keep in mind as we assess newborns with jaundice.