The probability that a Dpositive father is heterozygous or homozygous for the D locus can be calculated based on the father's Rh phenotype, his race, and the D status of his offspring. This can be used in evaluating the risk of antiD related Hemolytic Disease of the Newborn in a Dnegative mother.
Probability of D Locus Status in Common Rh Phenotypes
Common Phenotype 
White

Black




Heterozygous 
Homozygous 
Heterozygous 
Homozygous 
CcDe 
0.90 
0.10 
0.41 
0.59 
CDe 
0.09 
0.91 
0.19 
0.81 
cDEe 
0.90 
0.10 
0.37 
0.63 
cDE 
0.13 
0.87 
0.01 
0.99 
CcDEe 
0.11 
0.89 
0.10 
0.90 
cDe 
0.94 
0.06 
0.54 
0.46 
If a Dpositive father has had any Dnegative offspring, then the probability that he is heterozygous for the D antigen is 1.0.
The probability that the father is heterozygous for the D locus given the Rh phenotype and the number of Dpositive offspring is as follows:
Father is White
Phenotype 
n=0 
n=1 
n=2 
n=3 
n=4 
n=5 

CcDe 
0.90 
0.82 
0.69 
0.53 
0.36 
0.22 
CDe 
0.09 
0.047 
0.024 
0.012 
0.006 
0.003 
cDEe 
0.90 
0.82 
0.69 
0.53 
0.36 
0.22 
cDE 
0.13 
0.070 
0.036 
0.018 
0.009 
0.005 
CcDEe 
0.11 
0.058 
0.030 
0.015 
0.008 
0.004 
cDe 
0.94 
0.89 
0.80 
0.66 
0.49 
0.33 
Father is Black
Phenotype 
n=0 
n=1 
n=2 
n=3 
n=4 
n=5 

CcDe 
0.41 
0.26 
0.15 
0.080 
0.042 
0.021 
CDe 
0.19 
0.10 
0.055 
0.028 
0.014 
0.007 
cDEe 
0.37 
0.23 
0.13 
0.068 
0.035 
0.018 
cDE 
0.01 
0.005 
0.003 
0.001 
<0.001 
<0.001 
CcDEe 
0.10 
0.053 
0.027 
0.014 
0.0.007 
0.003 
cDe 
0.54 
0.37 
0.23 
0.13 
0.068 
0.035 
Calculating the Probability with Bayes Theorem
probability that the Dpositive father with a given Rh phenotype is homozygous for D =
= A / (A + B)
probability that the Dpositive father with a given Rh phenotype is heterozygous for D =
= 1  (probability homozygous)
where:
• A = (probability homozygous for D with Rh phenotype)
• B = ((probability heterozygous for D with Rh phenotype) * ((0.5) ^ 2))
This is derived with Bayes theorem:
P(DD  i and n) =
= [P(DDi) * P(nDD)] / [P(DDi) + {P(Ddi) * P(nDd)}]
where:
• i = Rh phenotype
• n = number of D positive offspring
• P(nDD) = 1
• P(nDd) = (0.5)^n
• P(DDi) = (probability homozygous for D with Rh phenotype)
• P(Ddi) = (probability heterozygous for D with Rh phenotype)
Specialty: Clinical Laboratory
ICD10: ,