A 34-week AGA neonate develops hyperbilirubinemia at 36 hours. Total serum bilirubin (TSB) is 14 mg/dL. Direct Coombs test is negative, blood group is B positive (mother is O positive). The neonate is breastfed. Which factor MOST increases the risk of bilirubin-induced neurologic dysfunction (BIND) at this bilirubin level?
- A Negative Coombs test
- B Gestational age of 34 weeks ✓
- C TSB crossing the high-intermediate risk zone
- D ABO incompatibility without hemolysis on smear
Correct answer: B. Gestational age of 34 weeks
Explanation
Late-preterm infants (34–36+6 weeks) have immature blood-brain barrier and lower albumin binding capacity, making them significantly more susceptible to BIND at bilirubin levels that would be tolerated by term infants. Phototherapy thresholds in the 2022 AAP guidelines are substantially lower for late-preterm compared to term infants. A negative Coombs test reduces hemolytic risk but does not lower BIND susceptibility. ABO incompatibility with a negative Coombs confers lower hemolysis risk than a positive Coombs.
Reference: Ghai Essential Pediatrics, 10th ed.
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