Physiological Jaundice of the Newborn
Physiological jaundice is a diagnosis of exclusion. It is a common, self-limiting condition resulting from the normal physiological transition of bilirubin metabolism after birth.
1. Diagnostic Criteria (The “Rules”)
- Onset: Appears after 24 hours of life.
- Peak: Usually peaks at 3–5 days in term infants.
- Duration: Resolves within 1–2 weeks.
- Bilirubin Levels: Rise is < 5 mg/dL per day, and peak unconjugated bilirubin remains within safe, age-appropriate limits (typically < 15 mg/dL in term infants).
2. Why it happens (Physiological Basis)
| Mechanism | Clinical Impact |
|---|---|
| High RBC Turnover | Shortened lifespan of fetal RBCs increases bilirubin load. |
| Immature Liver | Reduced UGT enzyme activity slows bilirubin conjugation. |
| Increased Enterohepatic Circulation | A sterile gut reduces the conversion of bilirubin to urobilinogen. |
3. Red Flags: When to Suspect Pathological Jaundice
- Early Onset: Jaundice in the first 24 hours of life.
- Rapid Rise: Increase in serum bilirubin > 5 mg/dL/day.
- Persistent Jaundice: Lasting > 2 weeks (term) or > 3 weeks (preterm).
- Conjugated Hyperbilirubinemia: Direct bilirubin > 2 mg/dL or > 20% of total bilirubin (always pathological; suggests cholestasis).
NEET PG Hint: Remember: Any jaundice appearing in the first 24 hours is pathological until proven otherwise. Always rule out ABO/Rh incompatibility. For more high-yield neonatology and free medical questions, visit mymedschool.org.