Yes.
If the mother's phenotype is A, the mother's genotype may be AA or AO.
If the mother's phenotype is A, the mother's genotype may be AA or AO.
If both are AO, the baby may inherit O from both parents, and the baby's genotype will be OO, and the phenotype will be O.
A baby born to two parents who are genotype AO can have the following genotypes: AA, AO, OO. The possible phenotypes are therefore A or O.