Two Rh+ parents,
an Rh− child?

The basic rule

Rh+ and Rh− usually refer to whether the RhD antigen is present. For teaching, it is described as one gene where D (present) is dominant over d (absent).

If both parents are Dd, each child has a 1 in 4 chance of being dd. So an Rh− child from two Rh+ parents is fully consistent with the rule.

Why frequency differs by population

Rh− is far more common among people of European descent than in East Asia. In Korea, for example, only about 0.1 to 0.3% of people are Rh−. Where the d allele is rare, an Rh+ parent is less likely to be a carrier, and two carriers having children together is rarer still.

Results by combination

Real RhD typing also has variants such as weak D and partial D that can make results unclear. Those details belong to a medical lab.

Check it in the app

The Android app Genetic Kids Lab treats Rh as a simple dominant/recessive trait and estimates whether an Rh+ parent is a carrier from a population frequency. That frequency is a simplified teaching value, so the app shows Rh− children more often than a low-Rh− population would. Use it to see where the 1 in 4 comes from.

1

Draw one child and read the card

Tap Draw one child to get a random virtual child. The Blood type (ABO) line shows ABO and Rh together, such as “A Rh+.”

2

Rh in the Punnett square

In the Genetics class tab, switch the Punnett square trait to Rh factor to see the Dd × Dd grid and its 3:1 ratio. Here a parent with the dominant type is assumed to be a carrier.

FAQ

Related guides

• Parents’ blood type chart for children, explainedAll 10 combinations · A × B can give any type · hidden O genes
• Traits that skip a generation — carriers, grandparents and sibling differencesHidden recessive alleles · 3-generation pedigree · same parents, different kids
• cis-AB blood type — the exception to the AB × O ruleA and B on one allele · about 0.035% of Koreans · retest first
• All Genetic Kids Lab guides10 guides in one place