What are the guidelines for bilirubin levels in newborns?

Bilirubin Level Guidelines in Newborns

All newborns ≥35 weeks gestation should undergo systematic risk assessment for severe hyperbilirubinemia, with treatment thresholds based on age in hours, gestational age, and presence of neurotoxicity risk factors using the AAP nomograms. 1, 2

Universal Screening and Risk Assessment

Every pregnant woman must be tested for ABO and Rh(D) blood types with serum screening for unusual isoimmune antibodies. 1, 2 If maternal blood type is unknown or Rh-negative, obtain direct antibody test (Coombs'), blood type, and Rh(D) type on cord blood. 2

Assess jaundice whenever vital signs are measured, but no less than every 8-12 hours. 2 Visual assessment alone is unreliable, particularly in darker-skinned infants—always obtain objective measurements with transcutaneous bilirubin (TcB) or total serum bilirubin (TSB). 3

When to Measure Bilirubin

Obtain TcB and/or TSB on every infant with jaundice in the first 24 hours after birth. 2 This is critical because jaundice presenting within 24 hours is pathologic and requires immediate evaluation. 4

For infants without early jaundice, TcB provides valid estimates when TSB is expected to be <15 mg/dL. 2, 3 However, for sick infants or those with jaundice at or beyond 3 weeks of age, measure both total and direct/conjugated bilirubin to identify cholestasis. 2, 5

Interpreting Bilirubin Levels

All bilirubin levels must be plotted according to the infant's age in hours (not days) on hour-specific nomograms. 3 For example, a 10-day-old infant is 240 hours old—this precision matters for treatment decisions.

Never subtract direct bilirubin from total bilirubin when making phototherapy or exchange transfusion decisions—use the total bilirubin value. 3 This is a critical pitfall that can lead to undertreatment.

Phototherapy Thresholds

The 2022 AAP guidelines raised phototherapy thresholds compared to previous recommendations, recognizing that kernicterus occurs at higher bilirubin levels than historically thought. 6, 7

Phototherapy thresholds vary by:

• Gestational age at birth (lower thresholds for 35-37 weeks vs ≥38 weeks) 3, 6
• Presence of neurotoxicity risk factors: hemolytic disease, G6PD deficiency, sepsis, acidosis, or albumin <3.0 g/dL 3
• Age in hours 2, 3

For healthy term infants without risk factors, general thresholds are approximately:

• 15 mg/dL at 25-48 hours 4
• 18 mg/dL at 49-72 hours 4
• 20 mg/dL after 72 hours 4

However, use the current AAP hour-specific nomograms for precise decision-making rather than these approximations. 6, 7

Pathologic Jaundice Indicators

Jaundice is pathologic if:

• Present within first 24 hours 4
• TSB rises >5 mg/dL per day 4
• TSB >17 mg/dL 4
• Signs/symptoms of serious illness present 4

Extended Laboratory Workup

If TSB is elevated or rising rapidly, obtain:

• Blood type and Coombs' test 3
• Complete blood count with peripheral smear 3
• Direct/conjugated bilirubin 3
• Reticulocyte count and G6PD level 3

For elevated direct/conjugated bilirubin, evaluate for:

• Urinary tract infection 5, 3
• Sepsis 5, 3
• Congenital hypothyroidism 5
• Galactosemia 5

Prolonged Jaundice (>3 Weeks)

All newborns with jaundice beyond 3 weeks require measurement of total and direct/conjugated bilirubin to identify cholestasis, plus verification of newborn screening results for thyroid and galactosemia. 5 Direct hyperbilirubinemia requires full investigation for cholestasis causes. 5

Breastfeeding Management

Advise mothers to nurse 8-12 times per day for the first several days. 1 Poor caloric intake and dehydration from inadequate breastfeeding contribute to hyperbilirubinemia development. 1

Do not routinely supplement nondehydrated breastfed infants with water or dextrose water—this will not prevent hyperbilirubinemia or decrease TSB levels. 1, 2 Continue frequent breastfeeding if the infant is clinically well and jaundice is mild to moderate. 5, 3

Follow-Up Timing

For infants with risk factors or rapidly rising bilirubin, recheck within 4-12 hours. 2 For stable infants without risk factors, recheck within 12-24 hours. 2 Infants with bilirubin approaching treatment thresholds need follow-up within 24 hours. 2

High-Risk Populations

Recognize that East Asian infants and those with G6PD deficiency have higher risk of significant hyperbilirubinemia. 3 Infants born at 35-37 weeks gestation also require lower treatment thresholds. 3, 6

Phototherapy Effectiveness

Phototherapy should produce a decrease >2 mg/dL within 4-6 hours. 2 Maximize effectiveness by increasing exposed skin surface area and minimizing physical obstructions like large diapers, head covers, and electrode patches. 2