In which scenario is Rh immunoglobulin administration required?

Rh immunoglobulin administration is essential in scenarios involving a Rh negative pregnant woman who may have experienced fetal-maternal hemorrhage due to trauma. This is particularly important to prevent Rh sensitization, which occurs when an Rh negative mother produces antibodies in response to Rh positive fetal blood cells entering her circulation. If the woman is Rh negative and has a positive pregnancy test, it indicates that she is likely at risk for potential complications if exposed to Rh positive blood.

In the context of trauma, particularly any situation where there may be bleeding or trauma to the abdomen, the risk of such hemorrhage increases. Therefore, in the presence of torso trauma, the administration of Rh immunoglobulin is warranted to protect against Rh sensitization. This is critical in preserving future pregnancies and preventing hemolytic disease of the newborn.

The other scenarios presented lack one or more critical components that necessitate the administration of Rh immunoglobulin. For instance, if the pregnancy test is negative or if the patient is Rh positive, the risk of sensitization is not a concern, and therefore, Rh immunoglobulin would not be indicated.