How is neonatal jaundice classified by timing and bilirubin type?

By timing: early-onset (within 2 weeks) versus prolonged (beyond 2 weeks in a term, 3 weeks in a preterm baby). By bilirubin type: unconjugated (can cross the blood-brain barrier and cause kernicterus) versus conjugated (always pathological, suggesting cholestasis - e.g. biliary atresia).

Clinical relevance. Classifying jaundice by timing and bilirubin type structures the differential and flags the urgent conjugated cases.

More Detail

Classification of neonatal jaundice

Classifying by timing and bilirubin type directs the differential diagnosis and urgency.

By timing

• Early-onset: within the first 2 weeks of life.
• Prolonged: persists beyond 2 weeks in a term baby (3 weeks in a preterm).

By bilirubin type

• Unconjugated (indirect) hyperbilirubinaemia: can cross the blood-brain barrier and, at high levels, deposit in the basal ganglia/thalami causing kernicterus.
• Conjugated (direct) hyperbilirubinaemia: always pathological, indicates cholestasis (e.g. biliary atresia) - needs urgent investigation.

Key rule

• Jaundice in the first 24 hours is always pathological (usually haemolysis).