Which intervention is necessary for an Rh positive infant born to an Rh negative mother postpartum?

The administration of gamma globulin, specifically Rh immunoglobulin (commonly known as RhoGAM), is a crucial intervention for an Rh positive infant born to an Rh negative mother. This situation arises when there is the potential for Rh incompatibility, which can lead to hemolytic disease of the newborn (HDN) if the mother has developed antibodies against Rh positive blood.

When an Rh negative mother carries an Rh positive child, the risk exists that when maternal and fetal blood mix, the mother may produce antibodies against the Rh factor. If this mother has already been sensitized in a previous pregnancy or blood transfusion, her immune system may attack the red blood cells of an Rh positive infant, leading to complications. Administering Rh immunoglobulin to the mother postpartum helps prevent her immune system from developing these antibodies, thereby safeguarding future pregnancies and the health of the current infant.

The other options provided are not necessary interventions in this specific scenario, as they do not address the issue of Rh incompatibility directly. Immediate intubation, isolation, and observation, as well as magnesium sulfate treatment, relate to different clinical situations and are not standard protocols for managing the implications of an Rh positive infant in this context.