Can two Rh-positive parents have an Rh-negative child?

July 10, 2013 at 2:46 pm

Your Rh status (positive or negative) is determined by an antigen found on your red blood cells (RBCs). Being Rh-positive or Rh-negative means that either you have the Rhesus D antigen on your RBCs or you don’t.

Rh status is inherited from our parents, separately from our blood type. If you inherit the dominant Rhesus D antigen from one or both of your parents, then you are Rh-positive (85% of us). If you do not inherit the Rhesus D antigen from either parent, then you are Rh-negative (15% of us).

So, is it possible for two people who are Rh-positive to produce a child that’s Rh-negative? The answer is yes—but only if neither parent passes along Rhesus D.

The simple Punnett square here demonstrates how this is possible.

Punnet square