Althought I understand that a rhesus A+ can donate blood to a rhesus A+, I don't really understand why a woman can donate blood to a man despite the compatibility of the blood group. As far as I know there are a lot of differences between women and men's blood. For example hormones, the concentration of red cells and platelets, etc. What about people who need a blood transfusion by week? Do physicians/nurses care about transfusing blood to a patient from a patient of the same sex? Or they don't even look at that?