Baby Blood Type Possibilities: Mother Type O, Father Type AB

Blood Type Inheritance Basics

Blood type is determined by the ABO gene, which has three alleles: IA (A antigen), IB (B antigen), and i (no antigen, type O). Each parent contributes one allele.

Parental Genotypes

• Mother (Type O): Genotype ii (two O alleles).
• Father (Type AB): Genotype IAIB (one A and one B allele).

Possible Offspring Genotypes & Phenotypes

The father can pass either IA or IB; the mother always passes i. Therefore, the child can only be:

• Type A (IAi) – inherits A from father, O from mother.
• Type B (IBi) – inherits B from father, O from mother.

Important: A child of this pairing cannot be type AB (requires IAIB) or type O (requires ii). The original source incorrectly listed AB and O as possibilities; the correct possible blood types are A and B only.

Summary Table

Father's Allele	Mother's Allele	Child's Genotype	Child's Blood Type
IA	i	IAi	A
IB	i	IBi	B

For personalized genetic counseling, consult a healthcare professional.