Neonatal Jaundice Phototherapy Threshold

Neonatal jaundice, or neonatal hyperbilirubinaemia, is the yellowing of skin and sclera caused by elevated serum total bilirubin (TSB) in the newborn period. It is one of the most common neonatal conditions, affecting approximately 60% of term and 80% of preterm neonates in the first week of life. In most cases, physiological jaundice is harmless and resolves without treatment, caused by the normal breakdown of foetal haemoglobin and the immature neonatal liver's limited conjugation capacity. However, severe untreated hyperbilirubinaemia can cause bilirubin to cross the blood-brain barrier, leading to acute bilirubin encephalopathy (ABE) and its chronic sequela, kernicterus — a devastating and entirely preventable cause of cerebral palsy, hearing loss, and intellectual disability. Clinical management centres on the Bhutani nomogram, which plots TSB against postnatal age in hours, defining risk zones (low, intermediate, high) and guiding phototherapy and exchange transfusion decisions. Crucially, treatment thresholds are adjusted downward for gestational age — a 35-week premature infant will require phototherapy at a much lower TSB than a term infant because the blood-brain barrier is more permeable and albumin binding capacity is lower. Phototherapy (specific wavelength blue light) converts unconjugated bilirubin into water-soluble photoisomers that can be excreted without conjugation. Exchange transfusion, which removes bilirubin directly from the circulation, is reserved for the most severe cases where phototherapy fails or bilirubin approaches critical levels. The BIND (Bilirubin-Induced Neurologic Dysfunction) score quantifies the clinical signs of acute bilirubin encephalopathy and guides urgency of exchange transfusion.

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1. 1Assess all neonates for jaundice at every examination in the first 5 days of life. Visual assessment alone is unreliable; any suspected jaundice within 24 hours of birth requires immediate transcutaneous or serum bilirubin measurement as this is always pathological.
2. 2Measure total serum bilirubin (TSB) or transcutaneous bilirubin (TcB) and record the exact postnatal age in hours at the time of measurement — not days, as hours matter for nomogram interpretation.
3. 3Plot the TSB value against postnatal age on the Bhutani nomogram (or a gestational age-adjusted chart as recommended by NICE or AAP). Identify whether the value falls in the low, low-intermediate, high-intermediate, or high-risk zone.
4. 4Determine the gestational age at birth and presence of risk factors that lower the treatment threshold: haemolysis (ABO/Rh incompatibility, G6PD deficiency), sepsis, hypoalbuminaemia, acidosis, or previous sibling requiring phototherapy.
5. 5Initiate phototherapy when TSB reaches the treatment threshold for the infant's gestational age and risk category. Position infant under conventional or LED phototherapy with maximum skin surface exposure and eye protection. Ensure adequate feeding.
6. 6Monitor TSB during phototherapy every 6-12 hours. Discontinue phototherapy when TSB falls at least 2 mg/dL (35 µmol/L) below the treatment threshold. Check rebound bilirubin 12-24 hours after stopping.
7. 7Escalate to exchange transfusion if TSB reaches the exchange threshold despite intensive phototherapy, if there are signs of acute bilirubin encephalopathy (hypertonia, opisthotonus, high-pitched cry), or if TSB rises at >0.5 mg/dL/hour despite phototherapy.

• !Relying on visual inspection of skin colour alone to assess jaundice severity — transcutaneous or serum bilirubin measurement is required for any clinical decision-making.
• !Recording postnatal age in days rather than hours when plotting on the Bhutani nomogram — the nomogram is calibrated in hours and using days will lead to incorrect risk zone classification.
• !Failing to adjust phototherapy and exchange thresholds downward for gestational age — treating a 35-week infant the same as a term infant risks under-treatment.
• !Stopping phototherapy prematurely without rechecking rebound bilirubin — TSB commonly rises 1-2 mg/dL within 12-24 hours of stopping phototherapy.
• !Not checking for G6PD deficiency or haemolysis in infants from high-prevalence ethnic groups (West African, Mediterranean, Middle Eastern, South Asian) with severe or rapidly rising jaundice.
• !Delaying exchange transfusion by attempting further phototherapy when clinical signs of acute bilirubin encephalopathy are already present — once opisthotonus and neurological signs appear, exchange is urgent.