AB blood is one of the ABO blood types, and mothers with AB blood need to know their father’s blood type in order to make a specific judgment. AB blood type is one of the ABO blood types, which contains both A and B antigens. Since the inheritance law of ABO blood type follows autosomal dominant or recessive inheritance, so the mother is AB blood type child, in the case of the father’s blood type is uncertain, the child’s blood type may be A, B, AB. AB blood type is a normal blood type, and its offspring’s blood type is also a normal blood type, so there is no need to worry too much. To know the exact blood type of a child, in addition to predicting it based on the parents’ blood type, a definitive test can be performed after birth, which is usually written on the birth certificate.