What's the cause of being jaundice in new born baby?

Neonatal jaundice. Increased bilirubin in the blood. Follow your doctors advice. The condition is usually temporary. Frequent breastfeeding sessions may help. Phototherapy may be used. Good luck.
See below. Newborn infant's liver is not mature enough to excrete bilirubin load to stool. This allows overflowing of yellow pigment (bilirubin) in blood and deposition of it in subcutaneous tissue.
Many Causes. In newborns there many factors that cause jaundice 1 breakdown of fetal hemoglobin as it is replaced by adult hemoglobin and there is relative immaturity of liver to conjugate the bilirubin to eliminate bilirubin as in adults, so it causes accumulation of bilirubin and jaundice(liver immaturity) 2blood group incompactibilities like ABO and rh 3biliary atresia 4alpha 1 antitrypsine def 5other liver.