Jaundice that appears during the neonatal period. In the majority of cases, it appears in the first week of life and is classified as physiologic due to accelerated destruction of erythrocytes and liver immaturity. In a minority of cases it is classified as non-physiologic, appearing in the first twenty four hours after birth, and is associated with underlying diseases including hemolytic disorders, polycythemia, and cephalohematoma. [from
NCI]