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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Physiological jaundice: appears day 2–3, peaks day 5, resolves by day 14 (21 in preterm) — immature hepatic conjugation + increased red cell breakdown
- Pathological: onset <24 h, rapidly rising, prolonged (>14 days term / >21 days preterm), or conjugated bilirubin >25 micromol/L
- Jaundice within 24 hours = ALWAYS pathological — urgent SBR, FBC, blood group, DAT (Coombs test)
- Management: plot total serum bilirubin on NICE CG98 threshold charts for gestational age — phototherapy if above treatment line
- Prolonged jaundice: check conjugated bilirubin — if raised (>25 micromol/L), investigate for biliary atresia urgently
- Kernicterus is the feared complication — irreversible brain damage from unconjugated bilirubin crossing the blood-brain barrier
Overview
Neonatal jaundice is extremely common, affecting approximately 60% of term and 80% of preterm neonates in the first week of life. It results from elevated unconjugated (indirect) bilirubin due to the physiological combination of increased red cell turnover, immature hepatic glucuronyl transferase activity, and increased enterohepatic circulation. Physiological jaundice is benign and self-limiting. Pathological jaundice — characterised by early onset (<24 h), excessive levels, prolonged duration, or conjugated hyperbilirubinaemia — requires investigation and treatment to prevent kernicterus.
Epidemiology
Approximately 60% of term and 80% of preterm neonates develop visible jaundice. Around 10% of breastfed infants remain jaundiced at 1 month. Risk factors for significant hyperbilirubinaemia include gestational age <38 weeks, previous sibling requiring phototherapy, exclusive breastfeeding with poor feeding, visible jaundice in first 24 hours, blood group incompatibility (ABO or Rhesus), G6PD deficiency, and bruising or cephalhaematoma. Kernicterus is rare in the UK (estimated 1 in 100,000 live births) but devastating when it occurs.
Clinical Features
Symptoms
Yellow discolouration of skin — progresses cephalocaudally (face to trunk to limbs)
Yellow sclerae — often the earliest and most reliable sign
Poor feeding or lethargy
Dark urine or pale stools (suggests conjugated hyperbilirubinaemia — biliary atresia)
Jaundice within 24 hours of birth
High-pitched cry, arching (opisthotonus), seizures — acute bilirubin encephalopathy
Signs
Jaundice visible on blanching the skin — harder to detect in darker skin pigmentation
Hepatosplenomegaly (suggests haemolytic cause)
Cephalhaematoma or extensive bruising (increased bilirubin load)
Signs of infection: temperature instability, poor perfusion
Hypertonia, retrocollis, opisthotonus (acute bilirubin encephalopathy)
Investigations
First-line
Serum total bilirubin (SBR)Gold standard — plot on NICE CG98 gestation-specific threshold chart. TcB can screen but confirm with SBR if near threshold
Maternal and baby blood group + DAT (Coombs)Essential if jaundice <24 h or rapidly rising — identifies ABO/Rhesus incompatibility
FBC and blood filmHaemoglobin, reticulocyte count, spherocytes (ABO incompatibility)
Second-line
Conjugated bilirubinMUST measure in prolonged jaundice. Conjugated >25 micromol/L = pathological — investigate for biliary atresia
G6PD assayConsider in unexplained significant jaundice — especially males and certain ethnic groups
TFTs and urine culturePart of prolonged jaundice screen — hypothyroidism and UTI are treatable causes
Specialist
Liver ultrasoundIf conjugated bilirubin raised — assess for biliary atresia (absent gallbladder, triangular cord sign)
HIDA scan / liver biopsyIf biliary atresia suspected — urgent surgical referral for Kasai portoenterostomy before 60 days
1
Assessment and monitoring
- Measure bilirubin in any visually jaundiced neonate — do not rely on visual assessment alone
- If jaundice within 24 h: urgent SBR, FBC, blood group, DAT
- Plot SBR on NICE CG98 gestation-specific treatment threshold chart
- Repeat SBR 6–12 hourly during phototherapy until falling and below threshold
2
Phototherapy
- Start if SBR above treatment threshold on NICE chart
- Single phototherapy first; escalate to intensive if SBR rising rapidly or near exchange threshold
- Continue breastfeeding during phototherapy — supplement if intake poor
- Stop once SBR 50+ micromol/L below threshold — recheck 12–18 h for rebound
3
Exchange transfusion
- If SBR above exchange transfusion threshold despite intensive phototherapy
- Urgent if clinical signs of acute bilirubin encephalopathy at any level
- Double-volume exchange transfusion (160 mL/kg) in NICU with continuous monitoring
4
Prolonged jaundice workup
- Investigate all neonates jaundiced beyond 14 days (term) or 21 days (preterm)
- Check conjugated and unconjugated split, TFTs, FBC, blood group, DAT, urine culture
- If conjugated bilirubin >25 micromol/L: urgent referral to exclude biliary atresia
- Breast milk jaundice is a diagnosis of exclusion — common cause of prolonged unconjugated jaundice in well, thriving breastfed babies
Complications
- Kernicterus: Irreversible damage to basal ganglia, brainstem, cerebellum — athetoid cerebral palsy, sensorineural hearing loss, upward gaze palsy
- Acute bilirubin encephalopathy: Lethargy, hypotonia progressing to hypertonia, opisthotonus, seizures — reversible if treated urgently
- Biliary atresia (if missed): Progressive liver fibrosis and failure if Kasai not performed before 60 days
- Anaemia: From haemolysis — may need top-up transfusion
UKMLA Exam Tips
- 1Jaundice within 24 hours = ALWAYS pathological — think haemolysis (ABO/Rhesus, G6PD)
- 2Use NICE CG98 threshold charts — they are gestation-specific, not weight-based
- 3Prolonged jaundice: the critical test is CONJUGATED bilirubin — raised >25 micromol/L means biliary atresia until excluded
- 4Breast milk jaundice causes prolonged UNCONJUGATED jaundice in a well, thriving baby — diagnosis of exclusion
- 5Pale stools + dark urine in a jaundiced neonate = conjugated hyperbilirubinaemia — biliary atresia until proven otherwise
- 6Kernicterus risk factors: prematurity, haemolysis, acidosis, hypoalbuminaemia
practicetest your knowledge on neonatal jaundiceApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — paediatrics and beyond.
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