Neonatal Jaundice — Phototherapy Threshold
TSB Units
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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.
Bhutani Nomogram: plot TSB (mg/dL or µmol/L) vs postnatal age (hours); phototherapy threshold varies by GA: term (≥38wk) ≈ 17-18 mg/dL at 72hr; 35wk ≈ 13 mg/dL at 72hr; exchange transfusion threshold ≈ 20-25 mg/dL depending on GA and risk factors; BIND score 0-9 (0-2 mild, 3-6 moderate, 7-9 advanced ABE)
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
Reassure parents; recheck TSB at 96 hours or earlier if jaundice appears to worsen
A TSB of 14 mg/dL at 72 hours in a term infant without risk factors falls in the low-intermediate zone. No phototherapy is needed but close follow-up is essential as bilirubin may continue to rise.
Start phototherapy; recheck TSB in 6-12 hours; continue aggressive feeding
Preterm infants have lower thresholds due to immature blood-brain barrier and albumin binding. A TSB that would be acceptable in a term infant may require phototherapy in a 35-weeker.
Rate of rise important: if rising >0.5 mg/dL/hour, prepare for exchange transfusion
Haemolytic jaundice (positive direct antiglobulin test) is a risk factor that effectively lowers the treatment threshold by one level. The rapid rate of bilirubin production requires more intensive monitoring than physiological jaundice.
Do not delay for phototherapy — exchange transfusion is the only definitive treatment at this stage
Clinical signs of advanced acute bilirubin encephalopathy alongside a critically high TSB demand emergency double-volume exchange transfusion (160 mL/kg) regardless of the rate of rise. Intensive phototherapy during the preparation period.
Neonatal ward universal bilirubin screening at 24-72 hours to identify infants at risk before clinical jaundice becomes severe., where accurate neonatal jaundice analysis through the Neonatal Jaundice supports evidence-based decision-making and quantitative rigor in professional workflows
Emergency department assessment of jaundiced neonates presenting after early discharge from maternity units., where accurate neonatal jaundice analysis through the Neonatal Jaundice supports evidence-based decision-making and quantitative rigor in professional workflows
NICU management of extremely preterm neonates with prophylactic phototherapy protocols to prevent bilirubin neurotoxicity., where accurate neonatal jaundice analysis through the Neonatal Jaundice supports evidence-based decision-making and quantitative rigor in professional workflows
Public health interventions: community midwife follow-up programmes using transcutaneous bilirubinometry to screen community-discharged neonates., where accurate neonatal jaundice analysis through the Neonatal Jaundice supports evidence-based decision-making and quantitative rigor in professional workflows
Research in low-resource settings: identifying appropriate phototherapy thresholds for populations with high G6PD prevalence where kernicterus remains a major cause of preventable disability.
G6PD Deficiency
G6PD deficiency can cause precipitous bilirubin elevation, especially on exposure to oxidant stressors (certain drugs, infections, fava beans in older children). In affected neonates, phototherapy thresholds should be set lower than for unaffected infants, bilirubin monitoring should be more frequent, and certain drugs (e.g., vitamin K1 in excess, some antibiotics) avoided.
Extreme Prematurity (<32 weeks)
Very preterm neonates are managed by NICU-specific gestational age-adjusted bilirubin charts that set much lower thresholds than term charts. The blood-brain barrier is highly immature and albumin levels are low, making kernicterus possible at TSB levels well below term thresholds. Phototherapy is often started prophylactically.
Conjugated Hyperbilirubinaemia
A direct (conjugated) bilirubin >1 mg/dL or >20% of TSB is always pathological and requires urgent investigation. Causes include biliary atresia (requires Kasai procedure before 60 days of age for best outcome), neonatal hepatitis, choledochal cyst, and metabolic disease. Phototherapy is not effective for conjugated hyperbilirubinaemia.
Hydrops Fetalis
Severe haemolytic disease of the newborn (e.g., anti-D) can cause hydrops fetalis with massive haemolysis requiring immediate exchange transfusion at birth. These infants may need intravascular intrauterine transfusion antenatally and have extremely high post-delivery bilirubin production. Specialist neonatology and haematology involvement is mandatory.
| Gestational Age | Phototherapy TSB (mg/dL) | Exchange Transfusion TSB (mg/dL) |
|---|---|---|
| ≥38 weeks, no risk factors | 17-18 | 25 |
| ≥38 weeks, with risk factors or haemolysis | 15 | 20 |
| 35-37 weeks + 6 days | 12-13 | 18-20 |
| 35 weeks | 11-12 | 17-18 |
| <35 weeks (preterm) | Per NICU gestational age-specific protocol | 15-17 |
What is the Bhutani nomogram?
The Bhutani nomogram is a risk stratification graph developed by Vinod Bhutani and colleagues that plots total serum bilirubin against postnatal age in hours for term and late-preterm newborns. It identifies high-, high-intermediate-, low-intermediate-, and low-risk zones. Measurements in the high-risk zone are strongly predictive of the need for phototherapy.
What is the difference between conjugated and unconjugated bilirubin?
Unconjugated (indirect) bilirubin is fat-soluble and can cross the blood-brain barrier to cause neurological damage. The liver converts it to water-soluble conjugated (direct) bilirubin, which is excreted in bile. Physiological neonatal jaundice involves unconjugated hyperbilirubinaemia. Conjugated hyperbilirubinaemia (>20% of TSB) always requires investigation as it indicates hepatobiliary pathology. This is particularly important in the context of neonatal jaundice calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise neonatal jaundice computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
How does phototherapy work?
Phototherapy uses blue-green light (peak wavelength 460-490 nm) to convert lipophilic unconjugated bilirubin into water-soluble photoisomers (lumirubin and configurational isomers) that can be excreted in bile and urine without hepatic conjugation. Efficacy depends on light intensity (irradiance), wavelength, and the area of skin exposed. This is particularly important in the context of neonatal jaundice calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise neonatal jaundice computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
When is exchange transfusion required?
Exchange transfusion is required when TSB reaches or is predicted to reach exchange threshold levels (typically 5 mg/dL above phototherapy threshold), when phototherapy fails to reduce TSB at the expected rate, or when clinical signs of acute bilirubin encephalopathy are present. Double-volume exchange (160 mL/kg) replaces approximately 90% of the infant's red cells and removes approximately 50% of circulating bilirubin.
What is the BIND score?
The Bilirubin-Induced Neurologic Dysfunction (BIND) score assesses clinical signs of acute bilirubin encephalopathy across three domains: mental status, muscle tone, and cry pattern. Each is scored 0-3. BIND 0-2 = subtle ABE; 3-6 = moderate ABE; 7-9 = advanced ABE. A BIND score of 7 or above is an indication for emergency exchange transfusion.
Why is jaundice within 24 hours of birth always pathological?
Physiological jaundice does not appear until after 24-36 hours of life because bilirubin production from fetal haemoglobin breakdown takes time to accumulate. Jaundice visible within the first 24 hours implies either haemolysis (ABO/Rh incompatibility, G6PD deficiency) or sepsis — conditions requiring urgent investigation and treatment. This is particularly important in the context of neonatal jaundice calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise neonatal jaundice computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
Can breast feeding cause jaundice?
Yes — two distinct patterns exist. Breastfeeding jaundice (early, days 2-5) results from insufficient milk intake causing dehydration and reduced bilirubin excretion. Breast milk jaundice (late, days 5-14) is caused by components in breast milk that inhibit bilirubin conjugation. The latter is benign and does not require cessation of breastfeeding. Management involves optimising feeding support and rarely temporary formula supplementation.
What is G6PD deficiency and why does it worsen jaundice?
G6PD (glucose-6-phosphate dehydrogenase) deficiency is an X-linked red cell enzyme defect that impairs the cell's ability to protect against oxidative stress. In affected neonates, red cell haemolysis is accelerated, dramatically increasing bilirubin production. G6PD deficiency can cause rapid, unpredictable bilirubin surges and is a major cause of kernicterus in countries where routine screening is absent.
プロのヒント
When a jaundiced neonate is discharged, always schedule a follow-up bilirubin check within 24-48 hours if the infant is under 5 days old. Bilirubin often peaks between days 3-5 in term infants and later in breastfed infants, so a normal TSB at discharge does not exclude subsequent pathological hyperbilirubinaemia.
ご存知でしたか？
Phototherapy for neonatal jaundice was discovered accidentally in 1956 by Sister Jean Ward, a nurse at Rochford General Hospital in Essex, England. She noticed that jaundiced babies taken outdoors into sunlight had less jaundice in exposed skin compared to areas covered by their nappies. She alerted Dr Richard Cremer, who then conducted the first clinical trials of phototherapy. This serendipitous observation has since prevented millions of cases of kernicterus worldwide.
参考文献
- ›AAP Clinical Practice Guideline — Hyperbilirubinemia in the Newborn Infant ≥35 Weeks' Gestation. Pediatrics 2022.
- ›Bhutani VK et al. Predictive ability of a predischarge hour-specific serum bilirubin for subsequent significant hyperbilirubinemia in healthy term and near-term newborns. Pediatrics 1999.
- ›NICE Guideline CG98 — Neonatal jaundice. 2010 (updated 2023).
- ›Kaplan M et al. G6PD deficiency and severe neonatal hyperbilirubinemia: a nationwide Israeli study. J Pediatr 2000.