When asked, many people do not know their blood type, but it is very important in a medical emergency that may require a blood transfusion or organ transplant. The study of blood is a particular specialty in medicine known as hematology . There are 29 different blood group systems, each represented by specific elements found on the surface of red blood cells. The most common blood group systems are ABO and Rhesus.
A person's blood type becomes a crucial issue when a blood transfusion is necessary. If an individual is transfused with the wrong type of blood, a reaction can occur that severely compromises the immune system. There are different levels at which mismatched transfusion can occur, from least to most incompatibility. Minor factors can lead to very minor problems, but a large blood type incompatibility during a transfusion can be serious.
Blood type is so important during a transfusion that donors who donate blood to a blood bank must meet certain requirements. A blood transfusion is closely monitored, often by a hematologist, and the ordering of blood products in the United States is regulated by the Food and Drug Administration.
In the case of organ transplants, the donor organ tissue must match the blood type of the recipient. A mismatch can cause rejection and therefore, without a positive match, the transplant will not proceed. People on the transplant waiting list undergo extensive blood type testing before being placed on the list.
Knowing one's blood type is also important for a pregnant woman and her fetus. A woman's blood type is usually determined during routine blood tests early in her pregnancy. In cases where the mother's type does not match the baby's, which are common, it is possible for the mother's body to develop antibodies to defend itself against the fetus's red blood cells. If these antibodies pass through the placenta, they can cause the baby to develop a blood disorder or disease. Although most complications of this situation range from mild to moderate, serious or even fatal reactions can occur.