A positive and B positive parents
Possible baby blood types: O+, O-, A+, A-, B+, B-, AB+, AB-.
| Child | Range | Typical |
|---|---|---|
| 0% – 25% | 18.1% | |
| 0% – 6.3% | 1.6% | |
| 0% – 50% | 24.9% | |
| 0% – 12.5% | 2.2% | |
| 0% – 50% | 20.5% | |
| 0% – 12.5% | 1.8% | |
| 18.8% – 100% | 28.3% | |
| 0% – 25% | 2.5% |
Range = lowest to highest chance across the genotypes each parent could carry. Typical = weighted by common allele frequencies. Try other inputs in the blood type calculator.
Why these results
An A positive parent carries ABO genes AA or AO and Rh genes DD or Dd. A B positive parent carries BB or BO and DD or Dd. Each passes one ABO gene and one Rh gene to the child at random.
ABO: every genotype pairing
| Parent 1 | Parent 2 | Child’s ABO group | Share of couples |
|---|---|---|---|
| AA | BB | AB 100% | 1% |
| AA | BO | A 50% · AB 50% | 14.9% |
| AO | BB | B 50% · AB 50% | 5.4% |
| AO | BO | O 25% · A 25% · B 25% · AB 25% | 78.7% |
Rh factor
| Parent 1 | Parent 2 | Child |
|---|---|---|
| DD | DD | Rh+ 100% |
| DD | Dd | Rh+ 100% |
| Dd | DD | Rh+ 100% |
| Dd | Dd | Rh+ 75% · Rh− 25% |
Step through any pairing on the blood type Punnett square.
Pregnancy and Rh
Both parents are Rh positive, so the mother does not need anti-D. The baby can still be Rh negative if both parents carry the hidden d gene.
Can these parents give each other blood?
A positive can receive red cells from O+, O-, A+, A-; B positive can receive from O+, O-, B+, B-. Full rules are on the blood type compatibility chart.
Frequently asked questions
What blood type will a baby of A+ and B+ parents have?
The child can be O+, O-, A+, A-, B+, B-, AB+, AB-. All eight types are possible. The most likely single type, using typical gene frequencies, is AB+ (about 28.3%).
Can A+ and B+ parents have a O+ child?
Yes. The chance is 0% – 25%, depending on the hidden genes each parent carries (about 18.1% with typical gene frequencies).
Can A+ and B+ parents have a O- child?
Yes. The chance is 0% – 6.3%, depending on the hidden genes each parent carries (about 1.6% with typical gene frequencies).
Can A+ and B+ parents have a A+ child?
Yes. The chance is 0% – 50%, depending on the hidden genes each parent carries (about 24.9% with typical gene frequencies).
Can A+ and B+ parents have a B+ child?
Yes. The chance is 0% – 50%, depending on the hidden genes each parent carries (about 20.5% with typical gene frequencies).
Does it matter which parent is the mother?
For the baby’s blood type, no. Each parent contributes one ABO gene and one Rh gene in the same way.