Usually before a blood transfusion the blood is cross checked of the blood being given and the blood group of the person before transfusion so as not to give the wrong blood group to the wrong person, apart from which the blood of the recepient and donor is mixed and observed for any changes. Incase of an ABO incompatibility reaction can occur if you receive the wrong type of blood during a blood transfusion. It’s a rare but serious and potentially fatal response to incompatible blood by your immune system.In an ABO incompatibility reaction, your immune system attacks the new blood cells and destroys them. The symptoms seen in a person with an ABO incompatability reaction are: - fever and chills - breathing difficulties - muscle aches - nausea - chest, abdominal, or back pain - blood in your urine - jaundice During an ABO incompatibility reaction, the red blood cells inside your circulatory system break down. Blood clotting may occur throughout your body, shutting off the blood supply to vital organs or causing a stroke. Too much blood clotting can use up clotting factors and leave you at risk of excessive bleeding. Some of the products released from broken-down blood cells can cause kidney damage and possibly kidney failure. An ABO incompatibility reaction can be life-threatening unless your doctor successfully treats it right away. However, if you have a reaction and receive the correct treatment without delay, you should recover completely.