Hyperbilirubinemia is an abnormally high level of bilirubin (a pigment produced from the breakdown of red blood cells) in the blood.
Aging red blood cells are normally removed by the spleen, and the hemoglobin (the oxygen-carrying substance) from these red blood cells is broken down and recycled. The heme portion of the hemoglobin molecule is converted into a yellow pigment called bilirubin, which is carried in the blood to the liver where it is chemically modified and then excreted in the bile into the digestive tract. It is removed from the body when the newborn passes stools.
In most newborns, the level of bilirubin in the blood increases in the first days after birth, and mild bilirubin elevations are considered normal. Bilirubin in the blood can cause the newborn's skin and the whites of the eyes to appear yellow (jaundice). If feedings are delayed for any reason, such as an illness or an intestinal problem, blood levels of bilirubin can become high. Also, breastfed newborns tend to have somewhat higher blood levels of bilirubin during the first week, but this increase also is usually of no concern. After several days, as the newborn takes more in feedings, the bilirubin level decreases.
Significant hyperbilirubinemia may occur when newborns have serious medical disorders, such as infection in the blood (sepsis). It may also be caused by the rapid breakdown of red blood cells (hemolysis), which occurs with Rh incompatibility (see Complications of Pregnancy: Rh Incompatibility) or ABO incompatibility (see Problems in Newborns: What Is Hemolytic Disease of the Newborn?).
In the large majority of cases, elevated levels of bilirubin in the blood are not serious. However, very high bilirubin levels can cause brain damage. Brain damage caused by hyperbilirubinemia is termed kernicterus. Very premature and critically ill newborns are at higher risk of developing kernicterus, but kernicterus usually can be avoided with appropriate treatment. However, newborns who are just a few weeks premature, who are breastfeeding, and who are discharged early from the hospital must be monitored closely for hyperbilirubinemia in the first few days after hospital discharge because they can develop kernicterus if the bilirubin level becomes very high. Premature newborns are at higher risk because they do not feed as vigorously as term infants and their mother's milk has not yet come in well.
Symptoms and Diagnosis
Newborns with hyperbilirubinemia have jaundice. It may be more difficult to recognize jaundice in dark-skinned newborns. Jaundice usually first appears on the newborn's face and then, as the bilirubin level increases, progresses downward to involve the chest, abdomen, and finally the legs and feet. But the appearance of jaundice does not provide an accurate measure of the bilirubin level.
The first symptoms of kernicterus are usually sluggishness (lethargy) and poor feeding. Newborns who have hyperbilirubinemia and these symptoms should be examined immediately by a doctor because they may need immediate treatment. The later stages of kernicterus involve irritability, muscle stiffening, arching of the back, seizures, and fever.
It is important that doctors assess the degree of jaundice in all newborns during the first days of life. Most doctors measure a newborn's bilirubin level before discharge from the hospital. Because bilirubin levels may take several days to rise to a dangerous level, newborns discharged from the hospital on the first day after birth should have their blood bilirubin levels checked at home by a visiting nurse or in the doctor's office within a few days after discharge. This testing is especially necessary for newborns born a few weeks prematurely who are breastfeeding.
Doctors first examine newborns under good lighting and then measure the level of bilirubin with a specialized piece of equipment held against the skin (transcutaneous bilirubinometer) or test a sample of blood.
Mild hyperbilirubinemia does not require special treatment. Frequent breastfeedings accelerate the passage of stools, thus reducing the reabsorption of bilirubin from the intestinal contents and lowering the bilirubin level.
Moderate hyperbilirubinemia can be treated with phototherapy, in which newborns are undressed and placed under bilirubin lights. The light exposure alters the composition of the bilirubin in the newborn's skin, changing it to a form that is more readily excreted by the liver and kidneys. The newborn's eyes are shielded with a blindfold because the lights may damage the eyes. Newborns can also be treated at home by having them lie on a fiber-optic bilirubin blanket, which exposes their skin to bright light. Newborns being treated with bilirubin lights need to have their blood levels of bilirubin tested repeatedly until the levels decrease because jaundice may disappear even though the levels of bilirubin in the blood remain elevated.
Very rarely, it may be necessary for a mother to change from breastfeeding to formula feeding for 1 or 2 days to ensure that the newborn is receiving enough with each feeding. The mother should resume breastfeeding as soon as the bilirubin levels start to decrease. Moderate hyperbilirubinemia sometimes continues for weeks in newborns who are breastfed, a normal phenomenon that poses no problems for the newborn.
If the newborn's bilirubin approaches a dangerous level even while phototherapy is used, the level can be lowered rapidly by doing an exchange blood transfusion. In this procedure, a sterile catheter is placed into the umbilical vein located in the cut surface of the umbilical cord. The newborn's bilirubin-containing blood is removed one syringe-full at a time and replaced with an equal volume of nonjaundiced blood provided by the blood bank.
Last full review/revision February 2009 by Arthur E. Kopelman, MD