Why would a newborn child get jaundice?

Transition work: Before birth the mothers body cleans all the babies blood & that stops at birth. The babies liver must gear up to breakdown & recycle proteins from the blood that can produce jaundice.Many issues can cause a backup of work & increase the jaundice. Over time the liver catches up with the work & jaundice fades .If the level gets high various rx are used to help bring it down.