Blood Grouping (Types of Blood) – The ABO & RH System

Noble Laureate Karl Landsteiner was involved in the discovery of both the ABO blood group (in 1901) and RH blood group (in 1937). There are more than 20 genetically determined blood group systems known today, but the ABO and RH systems aer the most important ones used for blood transfusions.  Not all blood groups are compatible  with each other. Mixing incompatible blood groups leads to blood clumping or agglutinations, which is dangerous for individuals.

Each person’s blood is one of four major types: A, B, AB or O.  Blood types are determined by the types of antigens on the blood cells. Antigens are proteins on the surface of blood cells that can cause a response from the immune system.

What is Rh factor? The Rh factor is a type of protein on the surface of red blood cells. Most people have the Rh factor – they are Rh-positive. Those who do not have the Rh factor are Rh-negative.

How does a person get the Rh factor? The Rh factor is inherited – passed down through parents’ genes to their children.

Can the Rh factor cause problems during pregnancy? The Rh factor can cause problems if you are Rh Negative and your foetus is Rh positive. This is called Rh incompatibility. These problems usually do not occur in a first pregnancy.

What happens if there is Rh incompatibility during pregnancy? When an Rh-negative mother’s blood comes into contact with blood from her Rh-positive foetus, it causes the Rh-negative mother to make antibodies against the Rh factor. These antibodies attack the Rh factor as if it were a harmful substance. A person with Rh-negative blood who makes Rh antibodies is called  ‘Rh sensitized’