Neonatal Jaundice: Physiological vs Pathological

Jaundice (yellow skin and eyes) is very common in newborn babies. Most cases are harmless "physiological" jaundice, but very high levels of unconjugated bilirubin can damage the brain (kernicterus), and some types of jaundice signal serious disease. Knowing when to worry is essential for every doctor who sees babies.

Why newborns get jaundice

Newborns break down red cells quickly, because they have a high red cell mass with a shorter lifespan. At the same time, their liver is still immature at conjugating bilirubin. Unconjugated bilirubin therefore rises in the first days of life.

Physiological versus pathological jaundice

• Physiological jaundice:
  • appears after 24 hours
  • peaks around days 3–5 in term babies
  • settles within about 2 weeks
  • the baby is well
• Pathological jaundice — suspect it if:
  • jaundice appears in the first 24 hours (always abnormal)
  • bilirubin rises rapidly or reaches treatment thresholds
  • the baby is unwell
  • jaundice is prolonged: more than 14 days in term babies, or more than 21 days in preterm babies
  • there are pale stools and dark urine, suggesting conjugated jaundice

Causes

• Early (under 24 hours):
  • haemolysis (Rh or ABO incompatibility)
  • G6PD deficiency
  • hereditary spherocytosis
  • congenital infection
  • sepsis
• Days 2 to 14:
  • physiological jaundice
  • breastfeeding-related jaundice (poor intake)
  • bruising or cephalohaematoma
  • polycythaemia
  • infection
  • haemolysis
• Prolonged:
  • breast milk jaundice (benign)
  • hypothyroidism
  • infection (including UTI)
  • haemolysis
  • conjugated causes, especially biliary atresia, which needs surgery (the Kasai procedure) early, ideally before about 6–8 weeks of age

Assessment

• Measure bilirubin. Visual inspection is unreliable, especially in darker skin. Use a transcutaneous bilirubinometer, or serum bilirubin in the first 24 hours or at high levels.
• Plot the level on a treatment threshold chart according to the baby's age in hours and gestation (for example NICE or AAP charts).
• Investigations for early, severe or prolonged jaundice:
  • blood group and direct antiglobulin (Coombs) test
  • full blood count and film
  • G6PD level
  • conjugated bilirubin
  • thyroid function
  • urine culture
  • infection screen if unwell
• Check stool and urine colour in prolonged jaundice.

Treatment

• Support feeding (breastfeeding support). Do not routinely give water or dextrose.
• Phototherapy when bilirubin is above the treatment threshold. Blue-green light converts bilirubin into water-soluble forms. Protect the eyes and monitor temperature and hydration.
• Exchange transfusion for very high levels or signs of bilirubin encephalopathy.
• IV immunoglobulin in selected cases of Rh or ABO haemolytic disease with rising bilirubin.
• Treat the underlying cause.

Kernicterus

Bilirubin encephalopathy presents with:

• lethargy and poor feeding
• a high-pitched cry
• abnormal tone
• arching of the back
• seizures

It can cause permanent cerebral palsy, deafness and learning difficulties. It is preventable with timely treatment.

Exam pearls

• Jaundice in the first 24 hours is always pathological.
• Pale stools and dark urine in a jaundiced baby: urgent conjugated bilirubin test, and consider biliary atresia.
• Always plot bilirubin against the baby's age in hours.

For more, see our Exam Night Rapid Revision Notes: Paediatrics 2.0.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Jaundice appearing in the first 24 hours of life is:

   1. Not important
   2. Always pathological
   3. Normal in preterm babies
   4. Always physiological
   5. Breast milk jaundice
   Show answer

   Answer: B. Always pathological
   Early jaundice suggests haemolysis or infection and needs urgent assessment.

2. Prolonged jaundice in a term baby is defined as lasting more than:

   1. 3 days
   2. 28 days
   3. 7 days
   4. 6 months
   5. 14 days
   Show answer

   Answer: E. 14 days
   More than 14 days in term (21 in preterm) babies.

3. Pale stools and dark urine in a jaundiced 4-week-old. Urgent concern?

   1. Dehydration
   2. Physiological jaundice
   3. Breast milk jaundice
   4. Biliary atresia
   5. Hypothyroidism only
   Show answer

   Answer: D. Biliary atresia
   Conjugated jaundice with pale stools needs urgent evaluation; Kasai surgery works best early.

4. How should a newborn's bilirubin level be interpreted?

   1. By skin colour alone
   2. Plotted on a threshold chart by age in hours and gestation
   3. By mother's blood group only
   4. By weight only
   5. Against adult ranges
   Show answer

   Answer: B. Plotted on a threshold chart by age in hours and gestation
   Treatment thresholds depend on age in hours and gestation.

5. Main treatment for bilirubin above the phototherapy threshold:

   1. Stopping feeds
   2. Phototherapy
   3. Vitamin K
   4. Water supplements
   5. Antibiotics
   Show answer

   Answer: B. Phototherapy
   Phototherapy converts bilirubin to water-soluble forms; exchange transfusion for very high levels.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.