The hemolytic disease of newborns (HDN) is one of the most significant risk factors for hyperbilirubinemia. Studies have shown that end-tidal carbon monoxide-corrected (ETCOc) correlated with the rate of bilirubin production in the body and thus can be a good surrogate to quantify hemolysis and identifying the high-risk infants. However, there is insufficient clinical evidence regarding the early prediction of hemolytic hyperbilirubinemia using ETCOc. This study hypothesizes that early postnatal ETCOc levels are significantly associated with the risk of hemolytic hyperbilirubinemia requiring treatments within 14 days after birth, and early postnatal ETCOc can be a good indicator for early prediction of hemolysis. In addition, the investigators aim to investigate the relationship between the characteristics of treatments for hyperbilirubinemia and ETCOc.