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Baby Blood Type Probability Calculator

Predict the probability of each blood type for your baby from the parents' ABO (and Rh) blood types.

Input

Estimates the probability of each possible blood type for your baby from the parents' ABO blood types. Possible genotypes for each phenotype are assumed equally likely.

Father's ABO blood type
Mother's ABO blood type

Result

Most likely blood type

Type AB

Probability56.3%

Probability of each possible blood type

Blood typeProbability
Type AB (most likely)56.3%
Type A18.8%
Type B18.8%
Type O6.3%

How it works

  • Calculates the probability of each possible blood type for a child from the father's and mother's ABO blood types, based on Mendelian inheritance.
  • ABO type is determined by combinations of three alleles (A, B, O). Type A has genotype AA/AO, type B has BB/BO, type AB has AB, and type O has OO; for each phenotype the possible genotypes are treated as equally likely.
  • From the alleles each parent can pass on, the probability (%) that the child is type A, B, O, or AB is shown in a table.
  • When the Rh factor is specified, the probability of Rh-positive and Rh-negative is also estimated (two Rh-negative parents can only have Rh-negative children).
  • If the parents' exact genotypes are known (for example from family history), the real probabilities will differ from this estimate, which is based on phenotype alone.
  • This tool provides genetic probabilities for reference only and is not a definitive prediction or medical advice. A laboratory test is required to confirm a blood type.