内容:Karl Landsteiner first thought of naming blood types in 1900. He put blood into four types. These four blood types were named A,B,AB and O.
Blood type O is the most common around the world. Blood type A is second most common , and type AB is the least common.
Doctors try to give blood to a person according to the person's blood type. Blood type O can be given to a person with any other blood type, but doctors prefer to match a patient's blood type if they can. Doctors also need to make sure that the"Rh factor"in patient's blood matches the blood they are given. If people have one kind of protein in their blood. they are positive(Rh+). If people do not have the protein, they are Rh negative(Rh-).Most people are Rh+.
If a mother has an Rh- blood type, she may have trouble when she has a baby. If her baby is Rh+,the baby's blood may mix with her mother's blood before the baby is born .The mother's blood will change. If the mother has another Rh+ baby ,the mother's blood will attack the baby's blood. The baby may die or become sick. Doctors have to watch the mother and baby carefully in these cases.
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