 This most often occurs when the mother has previously been exposed to blood antigens present on the fetus but foreign to her, through either a blood transfusion or a previous pregnancy.Because "in vivo" hemolysis destroys red blood cells, in uncontrolled, chronic or severe cases it can lead to hemolytic anemia.A hemolytic crisis, or hyperhemolytic crisis, is characterized by an accelerated rate of red blood cell destruction leading to anemia, jaundice, and reticulocytosis.