Which factor is crucial in determining whether a mother should receive RhoGAM after delivery?

The factor crucial in determining whether a mother should receive RhoGAM after delivery is the mother's blood type. RhoGAM, or Rh immunoglobulin, is administered to Rh-negative mothers who deliver an Rh-positive infant. This is important because if the mother is Rh-negative and the infant is Rh-positive, the mother's immune system may produce antibodies against the Rh factor found in the infant's blood. This can lead to serious complications in future pregnancies, including hemolytic disease of the newborn.

The administration of RhoGAM is a preventive measure that helps ensure the mother’s immune system does not become sensitized. Thus, identifying the mother's blood type is critical—if she is Rh-negative and the infant is Rh-positive, RhoGAM will be indicated. This intervention is not affected by factors such as the infant's weight, presence of jaundice, or the method of birth. These other factors may be relevant in different clinical contexts but are not decisive when it comes to RhoGAM administration.