Hour-Specific Total Serum Bilirubin Percentiles for Infants Born at 29-35 Weeks' Gestation

Introduction: As preterm infants are susceptible to hyperbilirubinemia, they require frequent close monitoring. Prior to initiation of phototherapy, hour-specific total serum bilirubin (TSB) percentile cut-points are lacking in these infants, which led to the current study.

Methods: A multi-site retrospective cohort study of preterm infants born between January 2013 and June 2017 was completed at 3 NICUs in Ontario, Canada. A total of 2,549 infants born at 290/7-356/7 weeks' gestation contributed 6,143 pre-treatment TSB levels. Hour-specific TSB percentiles were generated using quantile regression, further described by degree of prematurity, and among those who subsequently received phototherapy.

Results: Among all infants, at birth, hour-specific pre-treatment, TSB percentiles were 36.1 µmol/L (95% confidence interval [CI]: 34.3-39.3) at the 40th, 52.3 µmol/L (49.4-55.1) at the 75th, and 79.5 µmol/L (72.1-89.6) at the 95th percentiles. The corresponding percentiles were 39.3 μmol/L (35.9-43.2), 55.4 μmol/L (52.1-60.2), and 87.1 μmol/L (CI 70.5-102.4) prior to initiating phototherapy and 24.4 μmol/L (20.4-28.8), 35.3 μmol/L (31.1-41.5), and 52.0 μmol/L (46.1-62.4) among those who did not receive phototherapy. Among infants born at 29-32 weeks, pre-treatment TSB percentiles were 53.9 µmol/L (49.4-61.0) and 95.5 µmol/L (77.5-105.0) at the 75th and 95th percentiles, with respective values of 48.7 µmol/L (43.0-52.3), and 74.1 µmol/L (64.8-83.2) for those born at 33-35 weeks' gestation.

Conclusion: Hour-specific TSB percentiles, derived from a novel nomogram, may inform how bilirubin is described in preterm newborns. Further research of pre-treatment TSB levels is required before clinical consideration.