Calculate blood type compatibility, inheritance probabilities, and transfusion safety. Essential tool for genetics, medicine, and personal health awareness.
The ABO blood group system is determined by a single gene with three alleles: A, B, and O. Each person inherits two copies (one from each parent). Alleles A and B are co-dominant, while O is recessive. The Rh system is governed by the RHD gene: Rh-positive (Rh+) is dominant over Rh-negative (Rh-). This calculator uses Mendelian genetics to enumerate all possible genotype combinations and compute precise offspring probabilities.
| Parent 1 | Parent 2 | Child Possible Blood Types | Probability Range* |
|---|---|---|---|
| O | O | O | 100% |
| O | A | A or O | ~50% A, 50% O (if A parent is AO) or 100% A (if AA) |
| O | B | B or O | Variable depending on B parent genotype |
| O | AB | A or B | 50% A, 50% B |
| A | A | A or O | Approx 75% A, 25% O if both AO |
| A | B | A, B, AB, O | All four possible (25% each if both heterozygous) |
| A | AB | A, B, AB | 50% A, 25% AB, 25% B |
| B | B | B or O | 75% B, 25% O (both BO) |
| B | AB | A, B, AB | 50% B, 25% A, 25% AB |
| AB | AB | A, B, AB | 25% A, 50% AB, 25% B |
* Probabilities depend on hidden parental genotypes; our calculator computes the exact aggregated probability across all possible genotype combinations.
If an Rh- mother carries an Rh+ baby, her immune system may produce antibodies that attack red blood cells in a subsequent Rh+ pregnancy, leading to hemolytic disease of the newborn (HDN). This calculator estimates the probability of Rh+ offspring. Preventive treatment with Rho(D) immune globulin (RhoGAM) is highly effective. Early prenatal care is essential.
Distribution varies by population. For example, O+ is the most common worldwide (~37%), followed by A+ (~27%). Rh-negative individuals are rarer, especially in Asia (e.g., <1% in China) but more common in Europe (~15%). These frequencies influence blood bank supply and transfusion planning.
Bombay phenotype (hh): A rare recessive condition where individuals lack the H antigen, appearing as type O regardless of ABO genotype. They can only receive blood from other Bombay donors. Our calculator assumes standard ABO inheritance and does not account for such ultra-rare variants. Cis-AB and other chimeras exist but are extremely rare.
Karl Landsteiner discovered the ABO system in 1901, earning the Nobel Prize. The Rh factor was identified in 1937 by Landsteiner and Wiener. Understanding these systems has saved millions of lives through safe transfusion and prenatal care.
The Rh protein is produced if at least one RHD allele is present (Rh+). Rh- individuals have two recessive alleles (dd). For a child to be Rh-, both parents must carry the recessive d allele. The calculator accounts for the fact that Rh+ parents may be either DD (homozygous) or Dd (heterozygous). This yields realistic probabilities, especially important for prenatal care (Rh incompatibility).
Understanding Rh inheritance is critical for preventing hemolytic disease of the newborn (HDN). If an Rh- mother carries an Rh+ child, she may produce antibodies that affect subsequent pregnancies. This calculator highlights the probability of Rh+ offspring, empowering family planning and medical awareness. Always consult healthcare providers for Rh immunoglobulin prophylaxis when indicated.