What is the rate of bilirubin (bilirubin) decrease in a newborn?

Rate of Bilirubin Decrease in Newborns

With intensive phototherapy, bilirubin decreases at 0.5 to 1 mg/dL per hour in the first 4-8 hours when levels are extremely high (>30 mg/dL), with a 30-40% reduction in initial bilirubin by 24 hours for term infants ≥35 weeks gestation. 1

Expected Decline Rates by Clinical Scenario

Extremely High Bilirubin (>30 mg/dL)

• Decline of up to 10 mg/dL can occur within a few hours when intensive phototherapy is used 1
• Expect at least 0.5 to 1 mg/dL per hour decrease in the first 4-8 hours 1
• The most significant decline occurs in the first 4-6 hours of treatment 1

Standard Phototherapy Scenarios

• For infants ≥35 weeks gestation readmitted for phototherapy: intensive phototherapy produces a 30-40% decrement in initial bilirubin level by 24 hours 1
• With standard (non-intensive) phototherapy systems: expect a 6-20% decrease of initial bilirubin level in the first 24 hours 1

Factors Affecting Rate of Decline

The rate of bilirubin decrease depends on several key variables 1:

• Type and intensity of phototherapy used (intensive vs. standard)
• Surface area exposed to phototherapy
• Distance of light source from the infant
• Initial bilirubin level (higher levels decline faster initially)
• Underlying cause of hyperbilirubinemia (hemolytic vs. non-hemolytic)
• Gestational age (preterm infants may respond differently)

Clinical Pearls and Pitfalls

Maximizing Phototherapy Efficacy

• Remove the diaper when bilirubin approaches exchange transfusion range to maximize surface area exposure 1
• Line bassinet sides with aluminum foil or white cloth when rapid reduction is critical 1
• Use bassinet rather than incubator to allow lights to be positioned closer (within 10 cm) to the infant 1

Monitoring Considerations

• The most dramatic decline occurs in the first 4-6 hours, so early reassessment is critical 1
• Continuous phototherapy is essential when bilirubin approaches exchange transfusion levels 1
• For routine cases, phototherapy can be interrupted briefly for feeding or parental visits without significantly compromising efficacy 1

Common Pitfall

• Do not expect linear decline rates throughout treatment - the rate of decrease is fastest initially and slows as bilirubin levels fall 1
• Diurnal variation exists with morning bilirubin levels higher than evening levels, which should be considered when timing follow-up measurements 2

Stopping Phototherapy

• For readmitted infants (typically TSB ≥18 mg/dL): discontinue phototherapy when serum bilirubin falls below 13-14 mg/dL 1
• Rebound is rare in readmitted infants, but follow-up bilirubin measurement 24 hours after discharge is a clinical option 1
• For hemolytic disease or early discontinuation (<3-4 days old): obtain follow-up bilirubin within 24 hours after discharge 1