Can a baby have a different blood group from his parents?

Q: Can a baby be born with O negative blood group, if the father and the mother have a B positive blood group?

A:Yes. If the genotype of both the father and the mother blood groups is BO, the child can inherit O gene from both the parents and the blood group of the child can be O. Similarly if both the parents have genotype Dd for Rh system the child can be born with dd i.e. Rh negative. In short the O-.