Hyperbilirubinemia Due to Prematurity

Hyperbilirubinemia is a medical condition more commonly known as jaundice. Jaundice occurs when there is too much bilirubin in the blood stream. Babies born prematurely, defined as earlier than 36 weeks gestation, are at higher risk of having hyperbilirubinemia. Although jaundice in premature babies is usually mild, doctors strive to understand the underlying causes and provide treatment when necessary because if it worsens and is left untreated, it can become potentially dangerous.

What is Bilirubin?

• Bilirubin is the waste product produced when red blood cells are broken-down. It is an orange-yellow pigment that is produced in the spleen, transported to the liver and excreted in the bile. There are two types of bilirubin: unconjugated, which is the initial fat-soluble product released, and conjugated, which is the water-soluble form that is excreted from the body. Hyperbilirubinemia in premature babies is an excess of unconjugated bilirubin in the blood.

Causes

• In utero, a baby's red blood cells circulate with the mother's, therefore, the bilirubin is removed by the mother's liver. A newborn baby has an increased number of red blood cells. In addition, the red blood cells are used and renewed at a faster rate than an adult. This adds extra stress on a baby's body that is already trying to adjust to transporting and excreting the bilirubin.

  In addition, a newborn baby, especially a premature infant, may not have enough conjugating enzymes in the liver to efficiently conjugate the bilirubin. The unconjugated bilirubin remains in the blood stream causing the hyperbilirubinemia. There can also be other causes, including internal bleeding, infection, incompatibility of baby's and mother's blood, or a liver malfunction, but most infant jaundice, even in premature babies, is physiologic jaundice and will resolve after a few days to a week.

Symptoms

• The most prominent symptoms of hyperbilirubinemia are yellow skin and yellowing of the whites of the eyes. These symptoms typically appear between two and four days after birth and should be monitored by a doctor. If symptoms worsen or your baby exhibits listlessness, is not gaining weight or makes high-pitched cries, be sure to consult a doctor immediately.

Treatments

• Most mild hyperbilirubinemia will resolve without treatments within two to three weeks after birth. Some babies, especially premature babies, will require help to lower the bilirubin level. Phototherapy requires the baby to be placed under special lighting which will help the bilirubin to change shape and structure allowing it to be excreted. Phototherapy can also be done at home by placing an infant near sunlight coming through a window.

  For those infants that have hyperbilirubinemia due to blood incompatibility with the mother, intravenous immunoglobulin, which is a blood protein, will help to reduce the number of antibodies which are breaking down the blood cells and creating additional bilirubin. In cases of more severe hyperbilirubinemia, an exchange blood transfusion may be necessary. This involves removing small amounts of blood which dilutes the bilirubin, and then transferring that blood back into the baby.

Dangers

• Although hyperbilirubinemia is typically a mild condition, it can be dangerous. Bilirubin is toxic to the brain, so if blood containing too much bilirubin flows through the brain, it can result in acute bilirubin encephalopathy. Symptoms include listlessness, high-pitched cries, arching of the neck and back and fever. Acute bilirubin encephalopathy can cause permanent brain damage, called kernicterus. This condition can result in involuntary movements of the body, hearing loss, permanent upward glaze and intellectual impairment.