Yellowing of the skin, eyes, and membranes caused by too much bilirubin in the blood. Bilirubin is a yellowish pigment produced from the breakdown of red blood cells. Bilirubin is removed from the body largely by the liver. The mild jaundice that commonly occurs between the 2nd and 5th day of life in newborns is called physiological jaundice and is due to the newborn's immature liver function.