NoBlood

Hi there,
My fiance has recently visited her GP for a blood test and was advised that she had a blood type of A - which seemed to be rare. Apparently due to the fact that im of a positive blood type there are some complications that could take place if my wife was to get pregnant, and measures including injections will need to be taken so that no antibodies are formed that wil reject the + blood. This all seemed very confusing to me as the GP did not explain very well the situation. Any information would be greatly appreciated.