Blood type determination can, in certain cases, provide a clue for inferring or excluding paternity; however, only a DNA test offers 100% certainty. The result of a blood-type-based examination does not qualify as legal evidence in court proceedings.
The genetic rules of blood type inheritance
- Two parents with blood type 0 can only have a child with blood type 0.
- Two parents with blood type A can have a child with blood type A or 0.
- Two parents with blood type B can have a child with blood type B or 0.
- Parents with blood types A and B can have a child with blood type A, B, AB, or 0.
- Parents with blood types A and AB can have a child with blood type A, B, or AB.
- Parents with blood types A and 0 can have a child with blood type A or 0.
- Two RH- parents can only have an RH- child.
- Two RH+ parents, or one RH+ and one RH- parent, can have a child who is either RH- or RH+.
Using the tables below, you can see what blood type a child may have based on the parents' blood types.
The child's possible blood type based on the mother's and father's blood type
| Mother's blood type |
Father's blood type | |||
|---|---|---|---|---|
| A | B | AB | 0 | |
| A | A or 0 | A, B, AB, or 0 | A, B, or AB | A or 0 |
| B | A, B, AB, or 0 | B or 0 | A, B, or AB | B or 0 |
| AB | A, B, or AB | A, B, or AB | A, B, or AB | A or B |
| 0 | A or 0 | B or 0 | A or B | 0 |
The father's possible blood type based on the mother's and child's blood type
| Mother's blood type |
Child's blood type | |||
|---|---|---|---|---|
| A | B | AB | 0 | |
| A | A, B, AB, or 0 | B or AB | B or AB | A, B or 0 |
| B | A or AB | A, B, AB, or 0 | A or AB | A, B or 0 |
| AB | A, B, AB, or 0 | A, B, AB, or 0 | A, B, or AB | — |
| 0 | A or AB | B or AB | — | A, B or 0 |
