What blood type will a child have if one parent has AB blood type and the other has O blood type?

Blood type is inherited from one’s parents and remains unchanged throughout life. It refers to the antigen types present on the surface of blood components—including red blood cells, white blood cells, and platelets. The most widely recognized blood group systems are the ABO system (comprising A, B, AB, and O types) and the Rh system. So, what blood type will a child have if one parent is AB-type and the other is O-type? Below, we address this question.

What blood type will a child have if one parent is AB-type and the other is O-type?

Generally, children born to an AB-type parent and an O-type parent will be either A-type or B-type. This is because individuals with AB blood carry the AB genotype, while those with O blood carry the ii genotype. According to Mendel’s laws of inheritance, the possible genotypes for their offspring are Ai and Bi. The Ai genotype expresses as A blood type, and the Bi genotype expresses as B blood type—thus, the child’s blood type will be either A or B. Blood type is determined by combinations of three alleles: A, B, and O. In most cases, a child’s potential blood type can be predicted based on parental blood types. Chromosomally speaking, an O-type individual carries two O alleles (OO), whereas an AB-type individual carries one A and one B allele (AB). Therefore, possible genotype combinations for their offspring include AO and BO. Since the O allele is recessive, the child will always express either the A or B phenotype—never O or AB.

Additional Information: Which blood type combinations pose risks during pregnancy?

1. In general, individuals of any blood type can marry and have children. However, if the mother is O-type and the father is A-type, B-type, or AB-type, there is a risk of hemolytic disease of the newborn (HDN) due to ABO incompatibility. Specifically, maternal anti-A or anti-B antibodies (naturally occurring IgG antibodies in O-type mothers) may cross the placenta into the fetal circulation. After birth, affected newborns may develop hemolytic jaundice within 24 hours.

2. Pregnant women with O-type blood should undergo prenatal antibody screening and blood typing to allow for appropriate clinical management. Additionally, if the mother is Rh-negative and has previously received blood transfusions or undergone abortions, she may have developed anti-Rh antibodies. If her fetus is Rh-positive, this increases the risk of Rh-incompatibility hemolytic disease of the newborn. Therefore, appropriate prenatal testing is strongly recommended.

The above outlines the blood type possibilities for children born to an AB-type and an O-type parent. We hope this information is helpful.