Bilirubin is a yellow pigment formed during the normal breakdown of red blood cells. In newborns, its levels are particularly relevant because many babies experience jaundice, a yellowish discoloration of the skin and eyes, shortly after birth.
Bilirubin Basics in Newborns
Unlike adults, whose livers efficiently process bilirubin for excretion, newborns have a higher number of red blood cells that break down more rapidly. At the same time, a newborn’s liver is still developing and may not be fully efficient at processing and removing this increased bilirubin from the bloodstream. This temporary imbalance often leads to a buildup of bilirubin, causing “physiological jaundice.” This type of jaundice is typical, usually appears two to four days after birth, and resolves on its own within one to two weeks as the baby’s liver matures.
Interpreting Newborn Bilirubin Levels
A “normal” bilirubin level in a newborn is not a single universal number; it depends on factors like the baby’s age in hours, gestational age (whether full-term or premature), and any risk factors. Healthcare professionals typically measure bilirubin levels using a transcutaneous bilirubinometer (a non-invasive skin device) or a blood test for precise serum measurement. Blood tests often confirm higher readings from skin tests.
Medical professionals rely on specific charts, often called nomograms, to interpret bilirubin levels relative to a baby’s age in hours. For healthy, full-term newborns, general guidelines suggest that bilirubin levels should be:
- Below 6 mg/dL within the first 24 hours.
- Below 10 mg/dL between 24 and 48 hours.
- Below 12 mg/dL between 48 and 72 hours.
- Below 15 mg/dL after 72 hours.
These thresholds guide intervention, but treatment decisions consider the baby’s overall health and unique circumstances. Premature infants, or those with additional health concerns, often have lower bilirubin thresholds that may prompt earlier or more aggressive management.
Addressing Elevated Bilirubin
While mild jaundice is common and resolves without intervention, significantly elevated bilirubin levels can pose health considerations for newborns. The most observable symptom is yellowing of the skin, typically starting on the face and spreading downward to the chest, abdomen, and limbs. Other indicators of potentially concerning bilirubin levels include unusual sleepiness, difficulty waking for feeds, or poor feeding.
Excessively high bilirubin can cross into the brain, potentially causing kernicterus, a rare but serious condition with lasting neurological effects. Phototherapy, exposing the baby’s skin to special blue-green lights, is the primary treatment. This light changes bilirubin molecules into a form the body can more easily excrete through urine and stool. In rare, severe cases where phototherapy is insufficient, an exchange transfusion may be performed, replacing small amounts of the baby’s blood with donor blood to rapidly reduce bilirubin levels.
Monitoring and When to Seek Care
Parents should monitor their newborn for signs of jaundice at home. Observe the baby’s skin color in good, natural light for increasing yellowness, especially if it extends beyond the face or if the whites of the eyes appear yellow. Regular feeding helps the baby excrete bilirubin through frequent bowel movements.
Other signs that warrant immediate medical attention include:
- Unusual lethargy.
- Difficulty waking the baby for feedings.
- A weak or poor suck during feeding.
- A high-pitched cry.
Contact a healthcare provider if the baby develops a fever or if jaundice appears within the first 24 hours after birth. Follow-up appointments, especially for babies discharged early, are important for professional assessment of bilirubin levels and overall well-being.