For which maternal blood type is RhIg specifically indicated?

Rh immunoglobulin (RhIg) is specifically indicated for Rh-negative mothers who are carrying Rh-positive babies. The primary purpose of administering RhIg is to prevent Rh sensitization in the mother, which can occur when fetal Rh-positive blood cells enter the maternal circulation. This sensitization can lead to the production of anti-Rh antibodies, which can cause hemolytic disease of the newborn in future pregnancies.

In the context of the options provided, O-negative mothers are Rh-negative. This makes them at risk for Rh sensitization if they have an Rh-positive baby, making RhIg administration critical in this scenario. The aim is to protect subsequent pregnancies from complications arising from Rh incompatibility.

Other blood types listed, such as A-negative, B-positive, and AB-positive, either do not pose the same risk or do not require RhIg intervention. For example, A-negative is also Rh-negative and would require RhIg in a similar context as O-negative, while B-positive and AB-positive are Rh-positive and do not need RhIg since they do not face the risk of sensitization.