The natural history of jaundice in predominantly breastfed infants.

BACKGROUND AND OBJECTIVES Breastfed newborns are more likely to develop prolonged hyperbilirubinemia than those fed formula, but the prevalence of prolonged hyperbilirubinemia in a largely white, North American breastfed population is unknown. In this population, we documented the natural history of jaundice and the prevalence of prolonged hyperbilirubinemia, and we evaluated the utility of assessing the cephalocaudal progression of jaundice in office-based practices. METHODS We measured transcutaneous bilirubin (TcB) levels during the first month in 1044 predominantly breastfed infants ≥35 weeks of gestation and assigned a cephalocaudal zone score to each infant at the time of the TcB measurement. RESULTS TcB level was ≥5 mg/dL in 43% of infants at age 21 ± 3 days and 34% were clinically jaundiced. At 28 ± 3 days, the TcB was ≥5 mg/dL in 34% and 21% were jaundiced. There was a strong correlation between the TcB level and the jaundice zone score, but there was a wide range of TcB levels associated with each score. CONCLUSIONS Practitioners can be reassured that it is normal for 20% to 30% of predominantly breastfed newborns to be jaundiced at age 3 to 4 weeks and for 30% to 40% of these infants to have bilirubin levels ≥5 mg/dL. The jaundice zone score does not provide an accurate assessment of the bilirubin level, but a score of zero (complete absence of jaundice) suggests that the level is unlikely to be >12.9 mg/dL, whereas a score of ≥4 usually predicts a level of ≥10 mg/dL.