Paternity Determination by Blood Type

Blood type can be used to disprove paternity in many cases.

The ABO blood type charts below can be used to predict the possibilities of paternity.

The charts below can assist you to determine either:

    1. The ABO blood type of the child when the blood type of the father and the mother are known (top chart), or

    2. The ABO blood type of the father if the blood type of the child and the mother are known (bottom chart).

ABO Blood Type Calculator

ABO blood types can be complicated to understand. This is mostly due to the fact that the 'O-type' antigen is masked by the presence of an A- or B-type antigen. This is explained in the following chart, showing the different the genotypes that make up the blood types.

For example, two O blood type parents can produce a child with only O blood type. Two parents with A blood type can produce a child with either A or O blood types. Two parents with B blood type can produce a child with either B or O blood type. One parent with A and another with B can produce a child with A, B, AB or O blood types. If one parent has A and another has AB, they can either produce a child with A, B or AB blood types. If one parent has A and another has O, they can either produce a child with A or O blood types.

Rh Positive (Rh+) and Negative (Rh-) Blood Types

The Rh (+/-) factor is inherited separately from the ABO blood types. Similarly to the masking effect of the O gene in ABO blood types, the Rh negative (Rh-) gene is also masked by the presence of a Rh positive (Rh+) genotype. Therefore, a person may have a Rh + blood type and can still have an Rh - gene (See the chart below). Furthermore, 2 parents with Rh + blood types can have a child with Rh - blood type.