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A B and O are blood groups identified by the presence of a unique protein on the surface of a red blood cell. These groups are important in selecting donors for blood transfusion. There are 4 common blood types: A, B, O and AB. The RH factor describes a protein that is also present on the surface of red blood cells. The presence or absence of the RH protein makes the blood type + (if present) or - (if absent).
Blood type is essential knowledge for all pregnant women and is routinely tested for in pregnancy. Women that are RH negative require immunization with Rhogham medication during bleeding in pregnancy and at 28 weeks into a pregnancy.
The table below lists compatibility charts for blood groups and types.