No, Rhogam is NOT indicated when the fetus is Rh-negative and the mother is Rh-positive
Rhogam (Rh immune globulin) is only administered to Rh-negative mothers who are at risk of exposure to Rh-positive fetal blood cells—the scenario you describe is the reverse situation and requires no intervention.
Understanding the Fundamental Indication
The entire purpose of Rh immune globulin is to prevent an Rh-negative mother from developing antibodies against Rh-positive fetal red blood cells 1. The FDA-approved indication explicitly states: "The mother must be Rho(D) negative and must not already be sensitized to the Rho(D) factor. Her child must be Rho(D) positive" 1.
When the mother is Rh-positive and the fetus is Rh-negative, there is no immunologic incompatibility that could lead to hemolytic disease. The mother's immune system will not react against Rh-negative fetal cells because:
- The mother already possesses the Rh antigen on her own red blood cells 1
- Rh-negative fetal cells lack the D antigen entirely, so there is nothing "foreign" for the maternal immune system to recognize 2
- Hemolytic disease of the newborn only occurs when an Rh-negative mother produces anti-D antibodies that cross the placenta and attack Rh-positive fetal cells 1, 3
The Correct Clinical Scenario for Rhogam
Rhogam administration requires ALL of the following conditions 1, 4:
- Mother must be Rh-negative (D-negative)
- Fetus/infant must be Rh-positive (D-positive) or unknown
- Mother must not already be sensitized (no pre-existing anti-D antibodies)
Why This Matters Clinically
The mechanism of Rh alloimmunization involves fetal Rh-positive red blood cells entering the maternal circulation and triggering antibody production in an Rh-negative mother 1. These antibodies can then affect future Rh-positive pregnancies by crossing the placenta and destroying fetal red blood cells, leading to hemolytic disease, hydrops fetalis, or stillbirth 5.
In your scenario (Rh-positive mother, Rh-negative fetus), this pathophysiology cannot occur. An Rh-positive individual cannot become "sensitized" to the absence of an antigen.
Common Pitfall to Avoid
Do not confuse the direction of incompatibility. The critical question is always: "Is the mother Rh-negative?" If the answer is no, Rhogam is never indicated regardless of fetal blood type 1, 4. The only exception would be if a woman has "weak D" (Du-positive) status, in which case she should NOT receive anti-D 4.