From the Guidelines
Bilirubin levels typically peak within 120 minutes of phototherapy initiation, as evidenced by the photoconversion of the unconjugated bilirubin molecule in the microcirculation of the skin 1. When considering the natural peak of bilirubin in newborns, it is essential to differentiate between the effects of phototherapy and the natural progression of bilirubin levels.
- The natural peak of bilirubin in newborns occurs due to immature liver function and higher red blood cell turnover.
- Term infants typically experience a peak in bilirubin levels between 3 to 5 days of life, while preterm infants may see a peak between 5 to 7 days.
- The use of phototherapy, as described in the technical report 1, leads to a rapid decrease in excessive unconjugated bilirubin concentrations, with the majority of photoconversion occurring within 120 minutes.
- This rapid decline is crucial in reducing the risk of bilirubin neurotoxicity and the need for exchange transfusions, particularly in high-risk neonates.
- The report 1 highlights the importance of phototherapy in preventing severe hyperbilirubinemia, especially in neonates at high risk, and emphasizes the need for serial measurements of total serum/plasma bilirubin concentrations and screening for intrinsic risk factors.
From the Research
Bili Peak Timing
- The timing of the peak bilirubin level is not explicitly stated in the provided studies 2, 3, 4, 5, 6.
- However, it is mentioned that bilirubin levels typically peak between 3 to 7 days of life, but this information is not directly provided in the given studies.
- A study from 2000 3 measured serum bilirubin levels in healthy term newborns for the first 5 days of life and found that significant hyperbilirubinemia (bilirubin levels ≥17 mg/dL) occurred after 72 hours of life in 12.05% of cases.
- Another study from 2000 4 reported on cases of kernicterus in term and near-term infants in Denmark, but did not provide specific information on the timing of peak bilirubin levels.
- The other studies 2, 5, 6 discuss various aspects of neonatal hyperbilirubinemia, including treatment options and risk factors, but do not provide direct information on the timing of peak bilirubin levels.
Factors Affecting Bili Peak
- Several factors can influence the timing and level of peak bilirubin, including:
- Gestational age: Preterm infants are at higher risk for significant hyperbilirubinemia 5.
- Feeding patterns: Infants who do not feed well and lose more than 10% of body weight are at higher risk for significant hyperbilirubinemia 5.
- Hemolytic diseases: Infants with hemolytic diseases, such as spherocytosis or galactosaemia, are at higher risk for significant hyperbilirubinemia 4.