Why do normal newborns also have jaundice?

Neonatal jaundice is also known as neonatal hyperbilirubinemia, due to the short life span of red blood cells in newborns, bilirubin will be formed after death of red blood cells, insufficient metabolic bilirubin capacity of newborns will lead to bilirubin deposition in blood resulting in yellow skin staining, normal neonatal physiological jaundice will improve by itself within two weeks after birth.