<P> Pregnant women may carry a fetus with a blood type which is different from their own . In those cases, the mother can make IgG blood group antibodies . This can happen if some of the fetus' blood cells pass into the mother's blood circulation (e.g. a small fetomaternal hemorrhage at the time of childbirth or obstetric intervention), or sometimes after a therapeutic blood transfusion . This can cause Rh disease or other forms of hemolytic disease of the newborn (HDN) in the current pregnancy and / or subsequent pregnancies . Sometimes this is lethal for the fetus; in these cases it is called hydrops fetalis . If a pregnant woman is known to have anti-D antibodies, the Rh blood type of a fetus can be tested by analysis of fetal DNA in maternal plasma to assess the risk to the fetus of Rh disease . One of the major advances of twentieth century medicine was to prevent this disease by stopping the formation of Anti-D antibodies by D negative mothers with an injectable medication called Rho (D) immune globulin . Antibodies associated with some blood groups can cause severe HDN, others can only cause mild HDN and others are not known to cause HDN . </P> <P> To provide maximum benefit from each blood donation and to extend shelf - life, blood banks fractionate some whole blood into several products . The most common of these products are packed RBCs, plasma, platelets, cryoprecipitate, and fresh frozen plasma (FFP). FFP is quick - frozen to retain the labile clotting factors V and VIII, which are usually administered to patients who have a potentially fatal clotting problem caused by a condition such as advanced liver disease, overdose of anticoagulant, or disseminated intravascular coagulation (DIC). </P> <P> Units of packed red cells are made by removing as much of the plasma as possible from whole blood units . </P> <P> Clotting factors synthesized by modern recombinant methods are now in routine clinical use for hemophilia, as the risks of infection transmission that occur with pooled blood products are avoided . </P>

Where are the a b and rhesus antigens found