What postpartum intervention is necessary for an Rh negative mother with an Rh positive infant?

The administration of gamma globulin, specifically Rh immunoglobulin (often referred to by the brand name RhoGAM), is a necessary intervention for an Rh negative mother who has given birth to an Rh positive infant. This treatment is crucial because Rh immunoglobulin works to prevent the mother from developing antibodies against Rh-positive blood cells, which could pose risks in future pregnancies.

When an Rh negative mother is exposed to Rh positive blood (most commonly during delivery), her immune system can react by creating antibodies against the Rh factor. If these antibodies are present in subsequent pregnancies, they can cross the placenta and attack the red blood cells of an Rh positive fetus, leading to serious complications such as hemolytic disease of the newborn. Administering Rh immunoglobulin within 72 hours of delivery of an Rh positive infant effectively mitigates this risk by helping to eliminate any fetal Rh positive red blood cells that may have entered the mother's circulation, thus preventing the formation of maternal anti-Rh antibodies.

In contrast, the other options listed, such as the transfusion of packed red blood cells, antibiotic therapy, and immediate phototherapy, do not specifically address the immunological needs associated with an Rh negative mother and an Rh positive infant scenario. These interventions are