Neonatal Jaundice & Hyperbilirubinaemia

Neonatal jaundice is the most common clinical problem of the newborn period, affecting ~60% of term and ~80% of preterm babies. The crux of NEET PG questions is separating benign physiological jaundice from dangerous pathological jaundice, knowing the phototherapy/exchange thresholds, and recognising bilirubin encephalopathy (kernicterus) before it becomes irreversible.

Bilirubin metabolism — why neonates are predisposed

Unconjugated (indirect) bilirubin is a lipid-soluble breakdown product of haem. In the newborn, several factors converge to raise it:

1. Increased load → higher RBC mass (Hb ~17–18 g/dL), shorter neonatal RBC lifespan (~70–90 days vs 120), and more ineffective erythropoiesis.
2. Decreased conjugation → relative deficiency of hepatic UDP-glucuronosyltransferase (UGT1A1) in the first days.
3. Increased enterohepatic circulation → high intestinal β-glucuronidase, sterile gut, and delayed feeds deconjugate bilirubin so it is reabsorbed.

Bilirubin becomes clinically visible (jaundice) at serum levels > 5 mg/dL, progressing in a cephalocaudal direction (Kramer's rule): face (~5 mg/dL) → upper trunk (~10) → lower trunk/thighs (~12) → arms/legs (~15) → palms & soles (> 15 mg/dL). Conjugated (direct) bilirubin is water-soluble, non-neurotoxic, but always pathological when raised.

High-yield: Indirect bilirubin is neurotoxic and causes kernicterus; direct bilirubin is never neurotoxic but conjugated hyperbilirubinaemia (direct > 1 mg/dL or > 20% of total) is ALWAYS pathological and demands a workup for cholestasis (biliary atresia, neonatal hepatitis, sepsis, TORCH, metabolic).

Physiological vs Pathological jaundice

Feature	Physiological	Pathological
Onset	After 24 h of life (term), 48 h preterm	Within first 24 h (always pathological)
Peak	Day 3–4 (term), day 5–7 (preterm)	Any time, often early
Peak level	≤ 15 mg/dL (term), ≤ 17 (preterm)	Often > 15 mg/dL
Rate of rise	< 5 mg/dL/day (< 0.5 mg/dL/hour)	> 5 mg/dL/day (> 0.5 mg/dL/hour)
Type	Unconjugated	May be conjugated or unconjugated
Duration	Resolves by day 14 (term), 21 (preterm)	Prolonged > 2 (term) / 3 (preterm) weeks
Direct fraction	< 1 mg/dL	> 1 mg/dL / > 20% suggests cholestasis

High-yield: Any of these = pathological → jaundice in first 24 h; TSB rise > 5 mg/dL/day; TSB > 15 mg/dL (term); direct bilirubin > 1 mg/dL; clinical jaundice persisting > 2 weeks (term) or > 3 weeks (preterm).

Mnemonic for causes appearing within 24 h → think HAEMOLYSIS: Rh incompatibility, ABO incompatibility, G6PD deficiency, hereditary spherocytosis, and congenital infection. Jaundice on day 1 is haemolytic until proven otherwise.

Etiology by time of onset

Age at onset	Common causes
< 24 h	Rh & ABO haemolytic disease, G6PD deficiency, spherocytosis, concealed haemorrhage, sepsis, congenital (TORCH) infection
24–72 h	Physiological, sepsis, polycythaemia, cephalhaematoma/bruising, infant of diabetic mother
72 h–1 week	Sepsis, breastfeeding/breast-milk, cephalhaematoma resorption
> 1 week / prolonged	Breast-milk jaundice, hypothyroidism, biliary atresia, neonatal hepatitis, Crigler-Najjar, galactosaemia, UTI, pyloric stenosis

Rh vs ABO haemolytic disease

Feature	Rh incompatibility	ABO incompatibility
Mother / baby	Rh-negative mother, Rh-positive baby	O mother, A or B baby
First baby affected?	Usually spared (needs prior sensitisation)	Can affect first baby
Severity	Severe; hydrops fetalis possible	Usually mild–moderate
Direct Coombs (DCT)	Strongly positive	Often weakly positive / negative
Peripheral smear	Nucleated RBCs, polychromasia	Spherocytes prominent
Antibody	Anti-D IgG	Anti-A/anti-B IgG
Prevention	Anti-D immunoglobulin to mother	None

High-yield: Direct Coombs test (DCT) detects maternal antibody coating the baby's RBCs — strongly positive in Rh disease. ABO disease classically shows spherocytes on smear with a weak/negative Coombs. Rh disease spares the first pregnancy unless the mother was previously sensitised; ABO disease can hit the first baby.

Breastfeeding vs Breast-milk jaundice

Feature	Breastfeeding (early) jaundice	Breast-milk jaundice
Onset	2–4 days (first week)	After day 5–7, peaks 2nd week
Mechanism	Suboptimal intake → dehydration, ↑ enterohepatic circulation	β-glucuronidase / factors in milk ↑ enterohepatic circulation
Volume of feeds	Low (lactation failure)	Adequate, baby thriving
Management	Increase feeding frequency (8–12/day), support lactation	Continue breastfeeding; reassure; rarely brief interruption

High-yield: Breastfeeding jaundice = "not enough breast milk" (early, dehydration). Breast-milk jaundice = "something in the breast milk" (late, prolonged, thriving baby). Do not stop breastfeeding routinely for breast-milk jaundice.

Clinical features & danger signs

• Yellow discolouration of skin/sclera, best seen by blanching the skin in natural light.
• Pallor + hepatosplenomegaly → suggests haemolysis.
• Acute bilirubin encephalopathy (ABE) evolves in phases:
  • Early: lethargy, hypotonia, poor suck.
  • Intermediate: irritability, hypertonia, retrocollis (neck arching back), opisthotonus, high-pitched cry, fever.
  • Advanced: apnoea, seizures, coma — often irreversible.

Kernicterus (chronic) classic tetrad → (1) choreoathetoid cerebral palsy, (2) high-frequency sensorineural hearing loss, (3) gaze palsy (upward gaze paresis), (4) dental enamel dysplasia. Bilirubin deposits selectively in the basal ganglia (globus pallidus, subthalamic nucleus), hippocampus, and brainstem nuclei.

High-yield: Free unconjugated bilirubin crossing the blood-brain barrier causes kernicterus. Risk is increased by prematurity, acidosis, sepsis, hypoalbuminaemia, hypoxia, and drugs that displace bilirubin from albumin (sulphonamides, ceftriaxone). Avoid sulpha drugs and ceftriaxone in jaundiced neonates.

Diagnosis & investigation of choice

Stepwise approach → Clinical (Kramer) screen → Total Serum Bilirubin (TSB) with fractionation (direct/indirect) = investigation of choice for severity → if elevated, determine mechanism.

First-line "jaundice workup" when pathological:

1. TSB + direct/indirect fraction.
2. Blood group & Rh of mother and baby.
3. Direct Coombs test (DCT) on baby.
4. Haemoglobin, haematocrit, reticulocyte count, peripheral smear.
5. G6PD assay (especially Indian males, North-West India high prevalence).
6. Sepsis screen / urine culture if prolonged or unwell.
7. Thyroid profile and urine reducing substances (galactosaemia) if prolonged.

Transcutaneous bilirubinometer (TcB) is a useful screening (non-invasive) tool but must be confirmed with serum TSB before treatment; TcB is unreliable after phototherapy has started and at high levels.

High-yield: Plot TSB against age in hours (not days) on the Bhutani nomogram / AAP hour-specific nomogram — a value in the high-risk zone (> 95th percentile) predicts subsequent severe hyperbilirubinaemia. Always interpret bilirubin against postnatal age in hours, gestational age, and risk factors — never a single fixed number.

For prolonged/conjugated jaundice → ultrasound abdomen, HIDA scan, and liver biopsy to rule out biliary atresia (surgical emergency; Kasai portoenterostomy ideally before 8 weeks of age). A triangular cord sign on USG and absent gall bladder point to biliary atresia.

Management / treatment of choice

The two definitive modalities are phototherapy and exchange transfusion, guided by hour-specific nomograms (AAP 2004 / 2022, NNF India).

Phototherapy

• Mechanism: Blue-green light (wavelength 460–490 nm, peak ~450–460 nm) converts toxic unconjugated bilirubin in the skin to water-soluble photoisomers — structural isomer lumirubin (the major irreversible, rapidly excreted product) and configurational isomers — excreted in bile/urine without conjugation.
• Effectiveness depends on irradiance (intensive ≥ 30 µW/cm²/nm), surface area exposed, and proximity of light.
• Care: expose maximum skin, cover eyes, maintain hydration and temperature, monitor TSB.

High-yield: Phototherapy works best at ~450–460 nm (blue light); lumirubin is the principal photoproduct responsible for bilirubin clearance. Side effects: loose green stools, hyperthermia, dehydration, retinal damage (hence eye shields), and the "bronze baby syndrome" — seen with conjugated (cholestatic) hyperbilirubinaemia, where phototherapy is relatively contraindicated.

Exchange transfusion

• Removes bilirubin and antibody-coated RBCs; corrects anaemia. A double-volume exchange (2 × 80 mL/kg ≈ 160–170 mL/kg) replaces ~85–90% of circulating RBCs and removes ~50% of intravascular bilirubin.
• Indications: TSB above the exchange threshold on nomogram, signs of acute bilirubin encephalopathy, or rapid rise despite intensive phototherapy. In Rh disease, cord bilirubin > 5 mg/dL or cord Hb < 10 g/dL favours early exchange.
• Blood selection: Rh disease → Rh-negative, baby's ABO group (or O-negative) cross-matched against mother. ABO disease → O group, Rh-compatible with baby.
• Complications: thrombocytopenia, hypocalcaemia, hypoglycaemia, hyperkalaemia, NEC, sepsis, air embolism, arrhythmia, portal vein thrombosis.

Adjuncts

• IVIG (0.5–1 g/kg) in isoimmune (Rh/ABO) haemolytic disease reduces the need for exchange transfusion by blocking Fc-mediated haemolysis.
• Adequate hydration / feeding reduces enterohepatic circulation.
• Treat underlying cause (sepsis, hypothyroidism, etc.).
• Antenatal prevention of Rh disease: anti-D immunoglobulin to Rh-negative mothers at 28 weeks and within 72 h of delivery of an Rh-positive baby.

Management flow → Confirm with TSB + fraction → plot on hour-specific nomogram with risk factors → below phototherapy line: observe, feed, repeat TSB → at phototherapy line: intensive phototherapy + workup → at exchange line OR encephalopathy signs: prepare double-volume exchange transfusion + IVIG (if isoimmune) → treat cause.

Inherited conjugation defects (quick contrast)

Disorder	Defect	Bilirubin	Clinical
Crigler-Najjar type I	Absent UGT1A1	Severe unconjugated, kernicterus	Fatal without liver transplant; phenobarbitone does not respond
Crigler-Najjar type II (Arias)	Reduced UGT1A1	Moderate unconjugated	Responds to phenobarbitone
Gilbert syndrome	Mildly reduced UGT1A1	Mild unconjugated, episodic	Benign; worsens with fasting/stress
Dubin-Johnson	MRP2 export defect	Conjugated	Black liver, benign
Rotor	Storage defect	Conjugated	Benign, normal liver colour

High-yield: Crigler-Najjar type I = absent enzyme, no response to phenobarbitone, needs liver transplant. Type II improves with phenobarbitone (enzyme inducer). Both are unconjugated; Dubin-Johnson and Rotor are conjugated and benign.

Complications

• Acute bilirubin encephalopathy → progressing to kernicterus (chronic, irreversible).
• Sensorineural hearing loss (BAER abnormality may be the earliest sign).
• Choreoathetoid cerebral palsy, gaze palsy, dental dysplasia.
• Exchange-transfusion-related: hypocalcaemia, thrombocytopenia, NEC, infection.
• In haemolytic disease: anaemia (early and late hyporegenerative anaemia at 2–6 weeks, especially after IVIG/Rh disease), hydrops fetalis.

Key differentials

• Sepsis — can cause both unconjugated and conjugated jaundice; always screen the sick or prolonged-jaundice neonate.
• Biliary atresia vs neonatal hepatitis — both cause conjugated jaundice with pale stools; biliary atresia needs Kasai before 8 weeks.
• Hypothyroidism — prolonged unconjugated jaundice + lethargy, feeding difficulty, large fontanelle.
• Galactosaemia — jaundice + hepatomegaly + cataract + E. coli sepsis + urine reducing substances; stop lactose.
• Polycythaemia (IDM, delayed cord clamping, twin–twin transfusion) — plethora + jaundice.
• Cephalhaematoma / bruising — resorbing blood raises indirect bilirubin around day 3–5.

Recently asked / exam angle

• Coombs interpretation: "Day-1 jaundice, O+ mother, B+ baby, spherocytes on smear, weak DCT" → ABO incompatibility. "Rh-negative mother, second baby, strongly positive DCT, nucleated RBCs" → Rh isoimmunisation.
• Wavelength of phototherapy = 460–490 nm (blue light); principal photoproduct = lumirubin.
• Bronze baby syndrome occurs when phototherapy is given to a neonate with conjugated hyperbilirubinaemia.
• Bhutani nomogram plots TSB against age in hours; high-risk zone = > 95th percentile.
• Kernicterus site = globus pallidus / subthalamic nucleus (basal ganglia).
• Drugs displacing bilirubin from albumin (avoid): sulphonamides, ceftriaxone, salicylates.
• Crigler-Najjar type II responds to phenobarbitone; type I does not, needs liver transplant.
• Biliary atresia → conjugated bilirubin, triangular cord sign on USG, Kasai before 8 weeks.
• Double-volume exchange = 160–170 mL/kg (2 × blood volume); removes ~85% RBCs, ~50% bilirubin.
• Single-question favourites: "Earliest sign of kernicterus" → lethargy/poor feeding/hypotonia; "most sensitive early indicator of bilirubin toxicity" → abnormal BAER.

Rapid revision

1. Jaundice is visible at TSB > 5 mg/dL and spreads cephalocaudally (Kramer's rule).
2. Jaundice in the first 24 h is always pathological — haemolytic until proven otherwise.
3. Physiological jaundice: appears after 24 h, peaks day 3–4, resolves by 2 weeks, indirect, rise < 5 mg/dL/day.
4. Direct bilirubin > 1 mg/dL (or > 20%) = conjugated hyperbilirubinaemia = always pathological (think biliary atresia, sepsis, TORCH).
5. Rh disease spares the first baby, strong DCT, nucleated RBCs; ABO disease can hit the first baby, spherocytes, weak DCT.
6. Breastfeeding jaundice = early, too little milk; breast-milk jaundice = late, thriving baby — keep feeding.
7. Investigation of choice for severity = TSB with direct/indirect fraction, plotted on the hour-specific (Bhutani) nomogram.
8. Phototherapy uses 460–490 nm blue light; makes lumirubin; contraindicated (bronze baby) in conjugated jaundice.
9. Exchange transfusion for very high TSB or acute encephalopathy; double-volume = ~160 mL/kg; add IVIG for isoimmune disease.
10. Kernicterus = choreoathetoid CP + sensorineural deafness + upgaze palsy + enamel dysplasia; deposits in basal ganglia.
11. Avoid sulphonamides and ceftriaxone (displace bilirubin from albumin) in jaundiced neonates.
12. Crigler-Najjar I → no phenobarbitone response, liver transplant; CN-II and Gilbert are benign and inducible by phenobarbitone.