Severe hyperbilirubinemia is a condition marked by high levels of bilirubin in a newborn’s blood. Bilirubin, a yellow pigment, is a natural byproduct of the breakdown of red blood cells. While most newborns experience a mild and temporary form of jaundice—a yellowing of the skin and eyes—severe hyperbilirubinemia is a more serious state requiring medical attention. This elevation can occur because a newborn’s liver is not yet mature enough to efficiently process bilirubin.
Although serious, the condition is identifiable and treatable. With timely diagnosis and intervention, the risks associated with high bilirubin levels can be effectively managed.
Causes and Risk Factors
Bilirubin is released into the bloodstream during the natural recycling of old red blood cells. The liver then processes bilirubin, making it water-soluble for excretion. In newborns, this system is still developing, which can lead to a temporary buildup called physiologic jaundice that appears on the second or third day of life and resolves on its own.
Certain conditions can disrupt this process, causing bilirubin to rise to severe levels. A primary cause is blood group incompatibility, such as an Rh-negative mother with an Rh-positive baby or a type O mother with a type A or B baby. In these cases, maternal antibodies can attack the infant’s red blood cells, causing a surge in bilirubin.
Genetic factors also play a part. Inherited conditions like glucose-6-phosphate dehydrogenase (G6PD) deficiency are a notable risk. G6PD is an enzyme that protects red blood cells, and its deficiency makes them more susceptible to breaking down, releasing excess bilirubin. Variations in the UGT1A1 gene can also impair the liver’s processing ability.
Premature birth is another risk factor because a preterm infant’s liver is even less developed. Significant bruising from a difficult delivery or a cephalohematoma—a collection of blood under the scalp—can also increase bilirubin as the body breaks down the trapped blood.
Recognizing Severe Symptoms
The first sign of jaundice is a yellowing of a baby’s skin and eyes, which starts on the face and moves down the body. Parents can check for this by gently pressing on their baby’s forehead; if the skin appears yellow, it suggests jaundice. While mild yellowing is common, certain symptoms indicate the condition may be severe and require medical evaluation.
One of the most concerning signs is a change in behavior. A baby with severe hyperbilirubinemia may become extremely sleepy, lethargic, and difficult to wake for feedings. A poor feeding ability or a weak suck is another important warning sign.
Changes in an infant’s cry and body movements also signal a problem. A high-pitched, inconsolable cry is a distinct symptom. Unusual body movements, such as a persistent arching of the back and neck (opisthotonos) or sudden limpness, are neurologic signs that bilirubin may be impacting the central nervous system.
The Risk of Kernicterus
Untreated severe hyperbilirubinemia can lead to a rare but serious complication called kernicterus. This condition occurs when bilirubin levels become so high that it crosses the blood-brain barrier. Once inside, bilirubin can deposit in and stain brain tissue, particularly in areas like the basal ganglia and brainstem, causing irreversible damage.
The initial stage, acute bilirubin encephalopathy, presents with symptoms like lethargy, poor feeding, and changes in muscle tone. If not treated urgently, this can progress to the permanent damage known as kernicterus.
The long-term consequences are significant. The brain damage can lead to a form of cerebral palsy with uncontrolled movements, hearing loss or deafness, and vision problems like a permanent upward gaze. It can also cause improper development of tooth enamel and intellectual disabilities.
Medical Interventions
Diagnosis begins with a physical exam and is confirmed by measuring bilirubin levels. Providers may use a transcutaneous bilirubinometer, a non-invasive device that shines a light on the skin. If the reading is high, a serum bilirubin blood test is used for a definitive diagnosis.
The most common treatment for lowering bilirubin is phototherapy. The infant is placed under special blue-green lights wearing only a diaper and protective eye covers. This light energy converts bilirubin in the skin into a water-soluble form that the body can excrete through urine and stool, bypassing the liver.
In cases caused by blood type incompatibility, intravenous immunoglobulin (IVIG) may be used. This therapy infuses a blood product that helps block the maternal antibodies attacking the infant’s red blood cells, which in turn lowers bilirubin production.
For the most severe cases that do not respond to phototherapy, an exchange transfusion may be necessary. This procedure involves slowly removing the infant’s blood and replacing it with fresh donor blood. This process rapidly lowers bilirubin concentrations and removes the harmful antibodies.