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Predict possible blood types for a child based on parents' blood types.
Predict possible blood types for a child based on parents' blood types
Everything you need to know
Blood type is determined by genetic inheritance from both parents through the ABO blood group system and the Rh factor. Understanding blood type genetics helps you:
The two primary determinants of blood type are the ABO system and the Rh factor, which together create eight possible blood types.
Our blood type calculator determines possible blood types for your child:
Select Parent 1's Blood Type
Select Parent 2's Blood Type
View Possible Blood Types
The ABO system is based on two gene variants (alleles) that determine the presence of specific antigens on red blood cells.
Three possible alleles:
Dominance relationships:
| Blood Type | Genotype | Antigens | Antibodies |
|---|---|---|---|
| A | I^A I^A or I^A i | A antigens | Anti-B antibodies |
| B | I^B I^B or I^B i | B antigens | Anti-A antibodies |
| AB | I^A I^B | Both A & B antigens | No anti-A or anti-B |
| O | ii | No A or B antigens | Anti-A and anti-B antibodies |
Example 1: Type A parent (I^A i) × Type B parent (I^B i)
Possible combinations:
Possible children: A, B, AB, or O (all possible)
Example 2: Type O parent (ii) × Type O parent (ii)
Possible combinations:
Possible children: Only Type O (100% certain)
Example 3: Type AB parent (I^A I^B) × Type O parent (ii)
Possible combinations:
Possible children: Type A or Type B only
The Rh system is determined by the presence or absence of the RhD antigen on red blood cells.
Two alleles:
Dominance:
Example 1: Rh positive parent (Dd) × Rh positive parent (Dd)
Possible combinations:
Possible children: 75% Rh positive, 25% Rh negative
Example 2: Rh positive parent (DD) × Rh negative parent (dd)
Possible combinations:
Possible children: 100% Rh positive
Example 3: Rh negative parent (dd) × Rh negative parent (dd)
Possible combinations:
Possible children: 100% Rh negative
| Parent 1 | Parent 2 | Possible Children | Impossible |
|---|---|---|---|
| A × A | 1. O parent: A or O; 2. A parent: A or O | A, O | B, AB |
| A × B | A or B parent has O allele: A, B, AB, O | A, B, AB, O | None |
| A × AB | 1. A is I^A I^A: A, AB; 2. A is I^A i: A, B, AB | A, AB or A, B, AB | O |
| A × O | Always: A or O | A, O | B, AB |
| B × B | Similar to A × A | B, O | A, AB |
| B × AB | 1. B is I^B I^B: B, AB; 2. B is I^B i: B, A, AB | B, AB or A, B, AB | O |
| B × O | Always: B or O | B, O | A, AB |
| AB × AB | Always: A, B, AB | A, B, AB | O |
| AB × O | Always: A or B | A, B | AB, O |
| O × O | Always: O | O | A, B, AB |
| ABO | Rh | Blood Type | Percentage Population |
|---|---|---|---|
| O | + | O+ | 37% |
| O | - | O- | 6% |
| A | + | A+ | 34% |
| A | - | A- | 6% |
| B | + | B+ | 9% |
| B | - | B- | 2% |
| AB | + | AB+ | 4% |
| AB | - | AB- | 1% |
Note: Percentages vary significantly by ethnic group and geographic region.
| Type | Can Donate To | Can Receive From |
|---|---|---|
| O- | All (universal donor) | O- only |
| O+ | O+, A+, B+, AB+ | O-, O+ |
| A- | A-, A+, AB-, AB+ | A-, O- |
| A+ | A+, AB+ | A-, A+, O-, O+ |
| B- | B-, B+, AB-, AB+ | B-, O- |
| B+ | B+, AB+ | B-, B+, O-, O+ |
| AB- | AB-, AB+ | A-, B-, AB-, O- |
| AB+ | AB+ (universal recipient) | All |
Critical point: RBC transfusions require exact ABO and Rh matching. Wrong type causes severe immune reaction.
Scenario: Mother is Rh negative, Baby is Rh positive
First pregnancy: Usually safe. Sensitization (mother develops antibodies) may occur during delivery when fetal blood mixes with maternal blood.
Subsequent pregnancies: If mother has been sensitized, her anti-D antibodies can attack fetal red blood cells, causing:
RhoGAM is an injection of anti-D antibodies given to Rh negative mothers to prevent sensitization.
Given:
Effect: Prevents mother from developing anti-D antibodies that would harm future pregnancies.
| Situation | Risk Level |
|---|---|
| Rh- mother, Rh+ baby (first pregnancy, with RhoGAM) | Very low |
| Rh- mother, Rh+ baby (first pregnancy, NO RhoGAM) | Moderate |
| Rh- mother, Rh+ baby (second+ pregnancy, NOT sensitized) | Very low |
| Rh- mother, Rh+ baby (previously sensitized) | High—requires specialized care |
Beyond ABO and Rh, dozens of other blood group systems exist:
People with rare antigens can develop antibodies against common blood types, making transfusion difficult.
Parents: Mother is A+ (I^A i, Dd), Father is B+ (I^B i, Dd)
ABO possibilities:
Rh possibilities:
Possible children blood types:
Parents: Mother is O- (ii, dd), Father is B+ (I^B i, Dd)
Rh risk: Father is likely Dd, so 50% chance baby is Rh positive
Management:
No. Blood type is genetically determined and doesn't change. However, fetal blood can mix with maternal blood during delivery.
Yes, with proper medical care. First pregnancy is usually safe. RhoGAM after delivery prevents sensitization. Future pregnancies remain safe.
No. Two type O parents (both ii) can only pass i alleles, so child is always type O (ii).
No. AB parents (I^A I^B) can only pass I^A or I^B, never i, so type O is impossible.
AB+ is universal recipient (can receive all types). O- is universal donor. However, no type is inherently "better" for health.
No scientific evidence supports any correlation between blood type and personality, intelligence, or disease susceptibility (outside specific rare conditions). Blood type affects transfusion compatibility and pregnancy management, nothing else.
It's typically done at birth or during newborn screening in most hospitals. Knowing your children's types is useful for medical records and emergencies, but not essential unless there's an Rh incompatibility concern.
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