A positive and A negative parents
Possible baby blood types: O+, O-, A+, A-. Not possible: B+, B-, AB+, AB-.
| Child | Range | Typical |
|---|---|---|
| 0% – 25% | 12.6% | |
| 0% – 12.5% | 5% | |
| 37.5% – 100% | 58.8% | |
| 0% – 50% | 23.5% | |
| Not possible | — | |
| Not possible | — | |
| Not possible | — | |
| Not possible | — |
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. An A negative parent carries AA or AO and 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 | AA | A 100% | 2.5% |
| AA | AO | A 100% | 13.4% |
| AO | AA | A 100% | 13.4% |
| AO | AO | O 25% · A 75% | 70.7% |
Rh factor
| Parent 1 | Parent 2 | Child |
|---|---|---|
| DD | dd | Rh+ 100% |
| Dd | dd | Rh+ 50% · Rh− 50% |
Step through any pairing on the blood type Punnett square.
Pregnancy and Rh
If the mother is the A- parent, the baby could be Rh positive, so she is usually offered anti-D (RhoGAM) around 28 weeks and again after birth if the baby is Rh positive. If the mother is the Rh-positive parent, no anti-D is needed. See the Rh factor guide.
Can these parents give each other blood?
A positive can receive red cells from O+, O-, A+, A-; A negative can receive from O-, A-. Full rules are on the blood type compatibility chart.
Frequently asked questions
What blood type will a baby of A+ and A- parents have?
The child can be O+, O-, A+, A-. Under normal inheritance the child cannot be B+, B-, AB+, AB-. The most likely single type, using typical gene frequencies, is A+ (about 58.8%).
Can A+ and A- parents have a O+ child?
Yes. The chance is 0% – 25%, depending on the hidden genes each parent carries (about 12.6% with typical gene frequencies).
Can A+ and A- parents have a O- child?
Yes. The chance is 0% – 12.5%, depending on the hidden genes each parent carries (about 5% with typical gene frequencies).
Can A+ and A- parents have a A+ child?
Yes. The chance is 37.5% – 100%, depending on the hidden genes each parent carries (about 58.8% with typical gene frequencies).
Can A+ and A- parents have a A- child?
Yes. The chance is 0% – 50%, depending on the hidden genes each parent carries (about 23.5% with typical gene frequencies).
Does it matter which parent is the mother?
For the baby’s blood type, no. For pregnancy care, yes: if the mother is the Rh-negative parent and the baby could be Rh positive, she is usually offered anti-D (RhoGAM).