Hi, thanks for using healthcare magic There are consequences to such a union. IN term of blood groups sometimes when a female whose blood group is rhesus negative ( O neg or AB neg or A neg or B neg) marries a man whose group is rhesus positive ( O positive /AB positive/ B positive or A positive), issues can arise. When the woman conceives , some of the baby s blood may enter the blood stream and the female would react to it and form antibodies against it. Because of this , there may be problems with subsequent pregnancies. Other than this, the blood group does not matter. I hope this helps