What blood type will a child have if one parent has type A blood and the other has type B blood?

Blood type refers to the antigen types present on the surface of blood components. Many parents speculate about their unborn child’s blood type before birth. The commonly referenced “blood type” specifically denotes the type of specific antigens expressed on red blood cell membranes. Human blood type is inherited from one’s parents and remains unchanged throughout life. So, what blood type will a baby have if one parent has type A blood and the other has type B blood? Below, we address this question.

What blood type can a child have if one parent is type A and the other is type B?

A child born to one type A and one type B parent may have any of the four major blood types: A, B, AB, or O. Specifically, the type A parent may be either homozygous (AA) or heterozygous (AO); similarly, the type B parent may be either homozygous (BB) or heterozygous (BO). The O allele is recessive and thus “hidden” in heterozygous individuals. When passing blood type alleles to offspring, the type A parent may transmit either an A or an O allele, while the type B parent may transmit either a B or an O allele. Each parent contributes one allele, and the combination determines the child’s blood type. Consequently, all four blood types—AB, AO (i.e., type A), BO (i.e., type B), or OO (i.e., type O)—are possible in the offspring.

Knowledge Extension: Blood Type Inheritance Patterns

1. Parental blood types: A + A → Possible offspring blood types: A, O; Impossible: B, AB

2. Parental blood types: B + A → Possible offspring blood types: A, B, AB, O; None impossible

3. Parental blood types: B + B → Possible offspring blood types: B, O; Impossible: A, AB

4. Parental blood types: One or both parents are AB → Possible offspring blood types: A, B, AB; Impossible: O

5. Parental blood types: A + O → Possible offspring blood types: A, O; Impossible: B, AB

6. Parental blood types: B + O → Possible offspring blood types: B, O; Impossible: A, AB

7. Parental blood types: O + O → Possible offspring blood type: O; Impossible: A, B, AB

The above covers all essential information regarding the possible blood types of children born to type A and type B parents. We hope this information proves helpful. From a genetic perspective, human blood type remains constant throughout life. However, under certain exceptional circumstances, blood type may change—for example, following hematopoietic stem cell transplantation, or in conditions such as systemic lupus erythematosus or leukemia.