Exclusion criteria included infectious, metabolic, or hemolytic diseases (including porphyria, glucose 6-phosphate dehydrogenase deficiency, and ABO alloimmunization), positive Coombs’ test, high reticulocyte count, abnormal peripheral blood smear, occurrence of icterus within the first 24 hours, increased levels of direct serum bilirubin or maternal history of phenobarbital consumption before, during, or after child birth.