MT AAB Immunohematology Practice Test 2026 - Free Immunohematology Practice Questions and Study Guide

Maternal anti-D antibodies indicate Rh sensitization, and IgG anti-D readily crosses the placenta to bind the D antigen on fetal red cells. This triggers macrophage-mediated hemolysis in the fetus and newborn, causing fetal anemia and, after birth, hemolysis-related signs such as jaundice from elevated unconjugated bilirubin. The newborn’s red cells are typically coated with IgG against D, producing a positive direct antiglobulin test. This pattern is classic for Rh hemolytic disease of the newborn, distinguishing it from ABO HDN (which involves different antibodies and is usually milder) and from other incompatibilities like Kell, which would not be defined by anti-D. So the presence of maternal anti-D antibodies with an HDN‑suspected presentation points to Rh incompatibility as the underlying cause.