Neonatal jaundice and bilirubin treatment thresholds

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Bilirubin is produced from haem breakdown, circulates unconjugated bound to albumin, is conjugated in the liver and excreted in bile. Newborns produce more bilirubin and conjugate and excrete it less efficiently than older children.

Physiological jaundice usually appears after 24 hours, peaks over the next days and resolves as hepatic handling and feeding improve. Prematurity prolongs vulnerability because binding and conjugation are less mature.

Poor milk transfer increases enterohepatic circulation and dehydration-associated jaundice. Breast-milk jaundice can persist in a thriving, otherwise well infant, but that diagnosis must not bypass assessment for cholestasis or disease.

Haemolysis can overwhelm clearance and create a fast bilirubin rise. Causes include Rh or ABO incompatibility, G6PD deficiency, hereditary spherocytosis, bruising and cephalohaematoma.

Unbound unconjugated bilirubin can cross the blood-brain barrier and injure basal ganglia and auditory pathways. Risk depends on gestation, concentration, rate of rise, haemolysis and clinical instability, not colour alone.

Conjugated hyperbilirubinaemia is never physiological. Biliary atresia, neonatal hepatitis, infection, metabolic disease and parenteral-nutrition cholestasis need prompt investigation because delayed biliary referral worsens outcome.

Phototherapy converts bilirubin into water-soluble photoisomers that can be excreted without hepatic conjugation. Effective treatment requires the prescribed spectrum, irradiance, skin exposure and monitoring.

Exchange transfusion rapidly removes bilirubin and antibody-coated red cells but carries serious risks. It requires expert neonatal and transfusion support; preparation should begin before the threshold is crossed when trajectory is concerning.

Treatment charts are safety tools. Record gestational age, exact sampling time, value, chart used, threshold, action and next measurement so handover cannot detach a bilirubin number from its meaning.

Key points

Jaundice reflects bilirubin deposition. Most newborn jaundice is unconjugated and transient, but timing, trajectory and the baby's condition determine risk.
Never use one universal bilirubin number: plot serum bilirubin against exact age in hours on the NICE graph or table for the baby's gestational age.
For jaundice before 24 hours, measure serum bilirubin within 2 hours and repeat every 6 hours until below the treatment threshold and stable or falling.
At 24 hours or later, measure bilirubin within 6 hours. Visual assessment alone must not be used to estimate concentration.
Use serum bilirubin for babies below 35 weeks and for all babies within the first 24 hours. After 24 hours at 35 weeks or more, transcutaneous measurement may screen.
If transcutaneous bilirubin exceeds 250 micromol/L, confirm with serum. Confirm with serum whenever the value is at or above the relevant treatment threshold.
First-line treatment above the phototherapy threshold is phototherapy with irradiance, surface area and eye protection delivered according to the device protocol.
Intensify phototherapy when bilirubin rises faster than 8.5 micromol/L/hour, is within 50 micromol/L of the exchange threshold after 72 hours, or fails to fall within 6 hours.
Stop phototherapy once serum bilirubin is at least 50 micromol/L below the relevant phototherapy threshold; check rebound serum bilirubin 12–18 hours later.
Use double-volume exchange transfusion when the exchange threshold is reached or acute bilirubin encephalopathy is present, while continuing intensified phototherapy.
In Rh or ABO haemolytic disease, consider IV immunoglobulin 500 mg/kg over 4 hours only when bilirubin continues rising faster than 8.5 micromol/L/hour despite intensified phototherapy.
Do not stop breastfeeding routinely. Assess attachment and intake, support frequent effective feeding and add expressed milk or formula only for a defined clinical indication.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Physiological and feeding-related

High red-cell turnover, immature conjugation and increased enterohepatic circulation produce common unconjugated jaundice, amplified by poor milk transfer.

Haemolysis and bilirubin load

Rh or ABO antibodies, G6PD deficiency, membrane disorders, bruising and cephalohaematoma can substantially accelerate neonatal bilirubin production.

Infection and endocrine-metabolic disease

Sepsis, hypothyroidism, galactosaemia and other disorders may impair bilirubin handling or increase red-cell haem breakdown after birth.

Cholestatic disease

Biliary atresia, neonatal hepatitis, congenital infection, metabolic disease and parenteral nutrition can all cause pathological conjugated hyperbilirubinaemia.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Production exceeds clearance
High neonatal erythrocyte turnover and immature hepatic uptake and conjugation allow circulating unconjugated bilirubin to accumulate after birth.
2
Enterohepatic recycling
Slow intake and gut transit permit bilirubin deconjugation and intestinal reabsorption, increasing circulating concentration during ineffective feeding.
3
Neurotoxicity
Unbound unconjugated bilirubin crosses into brain and damages auditory and motor nuclei, progressing from subtle encephalopathy to permanent kernicterus.
4
Impaired bile flow
Obstruction or hepatocyte dysfunction retains conjugated bilirubin and bile constituents, producing dark urine, pale stool and malabsorption.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Visible jaundice

Examine sclera and skin in bright natural light, blanching the skin, but measure bilirubin whenever jaundice is suspected because visual estimation is unreliable across all skin tones.

Timing and history

Record onset in hours, gestation, feeding, weight change, urine and stool colour, alertness, temperature, bruising, cephalohaematoma, maternal and infant blood groups and family history.

Systemic examination

Assess pallor, hydration, hepatosplenomegaly, infection signs and neurological state, specifically suck, cry, tone, posture, apnoea and seizures.

Cholestasis clues

Ask whether stools are pale or chalky and urine persistently dark enough to stain the nappy; provide or use a stool-colour reference where available.

Bilirubin trajectory

Use the rate of rise from accurately timed serum samples; a fast increase suggests haemolysis or inadequate response and can trigger treatment intensification.

Bilirubin fraction

Distinguish unconjugated from conjugated bilirubin in prolonged jaundice or when cholestasis signs are present; phototherapy does not treat the underlying conjugated disorder.

Red flags requiring action

Visible jaundice before 24 hours requires urgent serum bilirubin measurement and medical review because haemolysis, infection and other pathology are more likely.
Lethargy, poor suck, altered tone, high-pitched cry, retrocollis, opisthotonus, apnoea or seizures raises acute bilirubin encephalopathy and possible urgent exchange transfusion.
A bilirubin at or above the gestation- and age-specific exchange threshold is an emergency even if the baby currently looks well.
Pallor, rapidly rising bilirubin, positive direct antiglobulin test, hepatosplenomegaly or family history raises haemolysis, including Rh, ABO or red-cell enzyme disease.
Dark urine that stains the nappy, pale stools, poor growth or hepatomegaly suggests conjugated jaundice and cholestasis rather than physiological unconjugated jaundice.
Prolonged jaundice beyond 14 days in a term baby or 21 days in a preterm baby needs assessment; conjugated bilirubin above 25 micromol/L requires expert advice.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line: bilirubin measurementFirst stepFirst line
Why
Quantify jaundice and determine treatment against the correct age- and gestation-specific threshold.
Interpretation and limitations
Use serum within 24 hours or below 35 weeks; transcutaneous screening is acceptable after 24 hours at 35 weeks or more, with serum confirmation above 250 micromol/L or at a treatment threshold.
02
Reference standard: serum bilirubin plotted on the NICE treatment graph or tableReference standard
Why
Decide phototherapy, intensified phototherapy, monitoring and exchange-transfusion action.
Interpretation and limitations
Use exact postnatal age in hours and gestation. No standalone universal concentration is safe; record both measured value and applicable threshold.
03
FBC, blood film, maternal and infant blood group and direct antiglobulin test
Why
Identify anaemia, haemolysis and immune incompatibility when bilirubin is early, rapid or clinically significant.
Interpretation and limitations
A positive DAT supports antibody coating but strength does not perfectly predict haemolysis; consider G6PD assay and other red-cell disease by ancestry and history.
04
Blood culture and infection assessment
Why
Detect sepsis when the baby is unwell, temperature unstable or has compatible maternal/perinatal risk.
Interpretation and limitations
Do not delay antibiotics in an unwell baby; jaundice can be a nonspecific manifestation of infection.
05
Prolonged-jaundice screen
Why
Detect cholestasis, haemolysis, infection, hypothyroidism and feeding or urinary disease.
Interpretation and limitations
Measure conjugated bilirubin, inspect stool and urine, obtain FBC, confirm blood group/DAT and review newborn blood-spot result; culture urine if clinically suspected.
06
Specialist hepatobiliary investigations
Why
Define biliary obstruction, infection or metabolic and genetic liver disease when conjugated bilirubin is raised.
Interpretation and limitations
Ultrasound, coagulation, liver tests, microbiology and metabolic testing are directed by neonatal hepatology; a normal ultrasound does not exclude biliary atresia.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Physiological or breast-milk jaundice

Later onset, a thriving well baby and reassuring investigations support benign physiology only after red flags are excluded.

Immune or non-immune haemolysis

Early onset, rapid rise, anaemia and reticulocytosis direct blood-group, DAT, blood-film and targeted red-cell enzyme assessment.

Sepsis or systemic disease

Poor feeding, instability, hepatosplenomegaly or abnormal examination requires prompt infection, endocrine and inherited metabolic disease assessment.

Conjugated cholestasis

Pale stool, dark urine and raised conjugated bilirubin distinguish impaired bile flow from common unconjugated disease.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Before 24 hoursUrgent pathological-jaundice pathwayFirst stepVisible jaundice appears in the first day.

1Measure serum bilirubin within 2 hours and arrange urgent medical review.
2Plot the value against exact age and gestation and investigate haemolysis, sepsis and other causes.
3Repeat at least every 6 hours until below threshold and stable or falling, treating according to trajectory.

02At or after 24 hoursMeasure and plotJaundice is visible in a baby aged at least 24 hours.

1Measure bilirubin within 6 hours using the gestation-appropriate method.
2Confirm qualifying transcutaneous results with serum and plot on the correct NICE chart.
3If below threshold, choose repeat timing from proximity, age, gestation, risk and trajectory; provide safety-netting.

03Above thresholdPhototherapy and escalationEscalationSerum bilirubin reaches a treatment line or rises concerningly.

1Start phototherapy at the chart threshold and investigate the cause.
2Recheck serum after 4–6 hours, then every 6–12 hours when stable or falling.
3Intensify for NICE criteria and prepare exchange transfusion early if approaching the exchange line or neurological signs appear.

04ProlongedExclude cholestasisJaundice persists beyond 14 days at term or 21 days preterm.

1Ask about pale stool and dark urine and assess growth and illness.
2Measure conjugated bilirubin and perform the NICE prolonged-jaundice investigations.
3Seek expert advice when conjugated bilirubin exceeds 25 micromol/L and refer urgently if biliary disease is suspected.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

Reduces antibody-mediated haemolysis and possible exchange-transfusion need in the narrow NICE-defined setting; it is not routine treatment for neonatal jaundice.

Intravenous human normal immunoglobulin

500 mg/kg intravenously over 4 hours as an adjunct to continuous intensified phototherapy for Rh or ABO haemolytic disease when serum bilirubin continues rising faster than 8.5 micromol/L/hour. Use the selected product's neonatal infusion protocol.

Confirm immune haemolytic disease and continue preparation for exchange transfusion. Monitor observations, urine output and infusion reactions; consider thrombosis, haemolysis, renal impairment and product-specific excipients. Dosing and preparation require senior neonatal and pharmacy oversight.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute bilirubin encephalopathy

Progressive feeding, tone, cry and conscious-level abnormalities can lead to seizures, coma and death without urgent treatment.

Kernicterus

Permanent bilirubin injury may cause dyskinetic cerebral palsy, auditory neuropathy, gaze disorder and characteristic later enamel dysplasia.

Exchange-transfusion harm

Catheter, electrolyte, haemodynamic, infectious and haematological complications require intensive neonatal monitoring, specialist performance and expert blood selection.

Delayed cholestasis diagnosis

Missed biliary atresia or metabolic liver disease delays time-sensitive intervention and can cause liver failure and malnutrition.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

During phototherapy measure serum bilirubin after 4–6 hours and then every 6–12 hours when stable or falling.
Document irradiance checks, skin exposure, eye protection, temperature, hydration, feeds, urine, stool and weight.
Use serum rather than transcutaneous measurements during and soon after phototherapy because light alters skin readings.
Stop treatment when at least 50 micromol/L below the phototherapy threshold and measure rebound serum bilirubin 12–18 hours later.
In haemolysis follow haemoglobin, reticulocytes and bilirubin after discharge because late anaemia may occur despite bilirubin control.
After acute bilirubin encephalopathy or exchange transfusion arrange neurological, developmental and formal audiology follow-up.
For conjugated jaundice monitor coagulation, fat-soluble vitamins, growth and liver disease through specialist care.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Age is measured in hours

A value just below a line now may cross it soon; the sample time, next threshold and rate of rise belong in every decision.

Colour cannot quantify

Visual inspection detects possible jaundice but does not reliably estimate bilirubin, particularly under artificial light or in darker skin.

Conjugated is different

Phototherapy targets unconjugated bilirubin; pale stool and dark urine point toward impaired bile flow requiring urgent causal investigation.

Feeding support is precise

Observe attachment and milk transfer, quantify output and weight trajectory, and preserve breastfeeding while treating insufficient intake when present.

Prepare before the line

A rapidly rising haemolytic bilirubin near exchange threshold warrants early neonatal and transfusion coordination rather than waiting for a final number.

11Common pitfallsFrequent interpretation and management errors.

01
Do not use visual colour to estimate bilirubin concentration.
02
Do not apply the 38-week graph to a more preterm baby or use age in days instead of hours.
03
Do not rely on a transcutaneous value within 24 hours, below 35 weeks or at a treatment threshold.
04
Do not call jaundice in the first 24 hours physiological.
05
Do not interrupt phototherapy repeatedly without accounting for lost treatment time.
06
Do not give IVIG for non-immune jaundice or without the NICE trajectory criterion.
07
Do not dismiss prolonged jaundice in a thriving breastfed baby without stool, urine and conjugated-bilirubin assessment.
08
Do not delay exchange-transfusion preparation when neurological signs or the relevant threshold is present.