In a healthy term newborn (≥37 weeks gestation) with jaundice and no risk factors, how should I evaluate for physiologic versus pathologic causes and what are the phototherapy thresholds, treatment steps, and indications for exchange transfusion or intravenous immunoglobulin?

Management of Newborn Jaundice in Healthy Term Infants

In a healthy term newborn (≥37 weeks) with jaundice and no risk factors, you should measure total serum bilirubin (TSB) or transcutaneous bilirubin (TcB) immediately if jaundice appears in the first 24 hours (always pathologic), plot the result on hour-specific nomograms to determine phototherapy need, initiate intensive phototherapy when TSB reaches age-specific thresholds (typically 12–15 mg/dL at 24–48 hours, 15–18 mg/dL at ≥72 hours for low-risk term infants), and prepare for exchange transfusion if TSB reaches ≥25 mg/dL or if any signs of acute bilirubin encephalopathy appear. 1

Initial Evaluation: Distinguishing Physiologic from Pathologic Jaundice

Timing Is Critical

• Jaundice appearing in the first 24 hours of life is always pathologic and demands immediate TSB or TcB measurement plus urgent evaluation for hemolytic disease—never discharge these infants without objective bilirubin measurement and a clear follow-up plan. 2
• Physiologic jaundice in term newborns typically begins after 24 hours, peaks between days 3–5, and resolves within 1–2 weeks. 2
• Never rely on visual assessment alone—it is dangerously unreliable, especially in darkly pigmented infants; always obtain objective TSB or TcB before making management decisions. 1, 2

Essential Laboratory Workup

When jaundice is present, obtain the following based on clinical context:

• For any infant jaundiced in the first 24 hours or with "excessive" jaundice for age: TSB, maternal and infant blood types, direct Coombs test (direct antibody test), complete blood count with peripheral smear, and reticulocyte count. 1
• When TSB ≥13 mg/dL: Add serum albumin measurement; if albumin <3.0 g/dL, calculate the bilirubin-to-albumin ratio because low albumin increases neurotoxicity risk. 1
• G6PD testing is indicated for infants of Mediterranean, African, Middle Eastern, or Asian descent, or when bilirubin rises despite phototherapy or rebounds after an initial decline—remember that G6PD levels can be falsely elevated during active hemolysis, so a normal result does not exclude deficiency. 1, 2
• If direct bilirubin is >1.0 mg/dL when TSB ≤5 mg/dL, or if direct bilirubin is >50% of total bilirubin, this indicates conjugated hyperbilirubinemia requiring specialist consultation for possible cholestasis. 1

Red Flags for Pathologic Jaundice

• Jaundice onset within the first 24 hours. 1, 2
• TSB rising by ≥0.3 mg/dL per hour during the first 24 hours or ≥0.2 mg/dL per hour thereafter—this signals active hemolysis and warrants urgent evaluation. 1, 2
• Isoimmune hemolytic disease (ABO or Rh incompatibility), G6PD deficiency, sepsis, significant cephalohematoma or bruising. 2
• Reticulocyte count ≥6% in a term or near-term infant should trigger immediate G6PD testing and evaluation for hemolytic etiologies. 1

Phototherapy Thresholds and Implementation

Hour-Specific Thresholds (Not Day-Based)

All bilirubin levels must be interpreted according to the infant's age in hours, not days, using hour-specific nomograms. 1, 2

• Term infants ≥38 weeks without risk factors: Phototherapy is indicated at approximately 12–15 mg/dL at 24–48 hours of life and 15–18 mg/dL at ≥72 hours. 1
• Medium-risk infants (≥38 weeks with risk factors OR 35–37 6/7 weeks, well): Use thresholds roughly 2–3 mg/dL lower than those for low-risk term infants. 1, 2
• High-risk infants (35–37 6/7 weeks with risk factors): Use the lowest threshold curve. 1, 2
• Beyond day 5–7 in healthy term infants, phototherapy is generally not indicated even if bilirubin exceeds conventional thresholds, because neurotoxicity risk declines sharply with postnatal age—exceptions include ongoing hemolysis, rapid bilirubin rise, or values approaching exchange-transfusion levels. 1

Risk Factors That Lower Treatment Thresholds

• Gestational age 35–37 6/7 weeks (especially important). 1
• Isoimmune hemolytic disease (positive direct Coombs, ABO or Rh incompatibility). 1
• G6PD deficiency. 1
• Neurotoxicity risk modifiers: sepsis, metabolic acidosis, serum albumin <3.0 g/dL, lethargy, temperature instability. 1

Intensive Phototherapy Technique

• Use blue-green LED light (wavelength 430–490 nm) delivering irradiance ≥30 µW/cm²/nm over the maximal body surface area. 3, 1
• Maximize skin exposure: Remove the diaper when bilirubin approaches exchange-transfusion levels, position the light source as close as safely possible, and line the bassinet with reflective material (aluminum foil or white cloth). 1
• Combine overhead phototherapy units with a fiber-optic pad placed beneath the infant to increase surface area exposure. 1
• Avoid physical obstruction of light by equipment, large diapers, head covers, eye masks, electrode patches, and insulating plastic covers. 3
• Change the infant's posture every 2–3 hours to maximize the area exposed to light. 3, 4

Expected Response to Phototherapy

• A normal response is a TSB decrease of >2 mg/dL within 4–6 hours of initiating intensive phototherapy. 3, 1, 4
• For extremely high bilirubin levels (>30 mg/dL), expect a decline of up to 10 mg/dL within a few hours and at least 0.5–1 mg/dL per hour in the first 4–8 hours. 1
• Failure of TSB to decrease or a continued rise despite intensive phototherapy signals ongoing hemolysis and requires immediate escalation of care, including G6PD testing and preparation for exchange transfusion. 1

Monitoring During Phototherapy

• Repeat TSB measurement within 2–3 hours if TSB ≥25 mg/dL, within 3–4 hours if TSB 20–25 mg/dL, and in 4–6 hours if TSB <20 mg/dL. 1
• Monitor continuously for signs of acute bilirubin encephalopathy: poor feeding, marked lethargy, high-pitched cry, abnormal muscle tone (hypotonia or hypertonia), opisthotonus, retrocollis, or fever. 1, 4
• Ensure adequate hydration, nutrition, and temperature control throughout treatment. 3
• Continue breastfeeding or bottle-feeding every 2–3 hours during phototherapy; supplement with formula or expressed breast milk for infants with signs of dehydration or weight loss >12% from birth. 1

Discontinuation of Phototherapy

• Stop phototherapy when TSB has fallen 2–4 mg/dL below the hour-specific threshold that prompted treatment initiation. 1
• For infants readmitted after birth hospitalization, discontinue phototherapy when serum bilirubin falls below 13–14 mg/dL. 1

Post-Phototherapy Follow-Up

• High-risk infants (phototherapy started <48 hours of age, gestational age <38 weeks, or positive direct Coombs/hemolytic disease) require TSB check 8–12 hours after cessation, followed by another measurement the next day. 1
• Standard-risk infants should have follow-up TSB within 1–2 days; TcB is acceptable if ≥24 hours have elapsed since phototherapy stopped. 1
• Rebound hyperbilirubinemia is rare but possible, especially in infants with hemolytic disease or those discharged before 3–4 days of age—these infants require 24-hour follow-up. 1

Exchange Transfusion Indications

Absolute Indications

• Any clinical signs of acute bilirubin encephalopathy (poor feeding, marked lethargy, high-pitched cry, hypotonia, hypertonia, opisthotonus, retrocollis, seizures, fever) constitute an absolute indication for exchange transfusion, regardless of the bilirubin level. 1
• These signs mandate immediate initiation of intensive phototherapy and preparation for exchange transfusion. 1

Bilirubin-Based Thresholds

• TSB ≥25 mg/dL is a medical emergency—the infant should be admitted directly to a pediatric service (not the emergency department) for immediate intensive phototherapy and preparation for exchange transfusion. 1
• If TSB ≥20 mg/dL in a sick infant or infant <38 weeks gestation, obtain blood type and crossmatch in preparation for possible exchange transfusion. 1
• Consider exchange transfusion if TSB is in the intensive phototherapy range and phototherapy does not promptly lower the TSB. 4

Important Context

• Exchange transfusion carries a mortality risk of approximately 3 per 1,000 procedures and significant morbidity in 5% of cases, but is life-saving when acute bilirubin encephalopathy is present. 1

Intravenous Immunoglobulin (IVIG)

• For isoimmune hemolytic disease, administer IVIG (0.5–1 g/kg over 2 hours) if bilirubin continues to rise despite intensive phototherapy or is within 2–3 mg/dL of the exchange-transfusion threshold. 1
• This intervention can reduce the need for exchange transfusion in cases of ABO or Rh incompatibility. 1

Hydration and Feeding Management

• Continue breastfeeding with 8–12 feedings per day for the first several days to promote bilirubin elimination. 4
• Avoid routine supplementation of nondehydrated breastfed infants with water or dextrose water—it will not prevent hyperbilirubinemia. 4, 2
• Milk-based formula can help lower serum bilirubin by inhibiting the enterohepatic circulation of bilirubin. 1

Critical Pitfalls to Avoid

• Never discharge infants born at 35 weeks gestation before 48 hours of life without guaranteed follow-up. 1
• Do not subtract direct (conjugated) bilirubin from total bilirubin when making treatment decisions, unless the direct fraction is ≥50% of the total (which requires specialist consultation). 1, 4, 2
• Do not ignore prolonged jaundice beyond 2–3 weeks; obtain total and direct bilirubin measurements and verify normal thyroid screening to rule out cholestasis or hypothyroidism. 1
• Remember that G6PD deficiency often causes a late-rising bilirubin peak (typically after day 3–5), especially in male infants of Mediterranean, Middle Eastern, African, or Asian descent. 1, 2
• Do not postpone phototherapy while awaiting laboratory results if the infant's TSB meets or exceeds treatment thresholds—phototherapy decisions are based on hour-specific TSB levels, not laboratory values. 1
• Do not use sunlight exposure as a reliable therapeutic tool. 1

Parent Education and Warning Signs

• Educate parents about signs of worsening jaundice and acute bilirubin encephalopathy: altered feeding patterns, extreme lethargy, high-pitched crying, abnormal muscle tone (stiffness or floppiness), arching of the back or neck, fever, or temperature instability. 1
• Parents should seek immediate medical care if any of these signs appear. 1