Final answer:
The Coombs test, specifically the indirect Coombs' test or indirect antiglobulin test (IAT), is used to assess the risk of isoimmune hemolytic anemia by detecting antibodies against fetal red blood cell antigens in the mother's serum.
Step-by-step explanation:
The test used to assess for fetal blood type and RBC count in the risk of isoimmune hemolytic anemia is the Coombs test. Specifically, it is the indirect Coombs' test, also known as the indirect antiglobulin test (IAT). This test screens for antibodies against red blood cell antigens that are unbound in a patient's serum, which can cause hemolytic disease of the newborn. A blood sample is taken from the patient and a few drops of Coombs' reagent, which contains antihuman antibodies, is mixed with the sample. If the patient's serum has antibodies, hemagglutination will occur indicating a positive test result.
The IAT is critical in obstetric care to prevent complications such as jaundice in newborns caused by the lysis of red blood cells due to mother's antibodies. This is why pregnant women are routinely screened for such antibodies to manage any potential risks to the fetus.