In blood type incompatibility during pregnancy, the fetal and maternal blood types differ, and maternal antibodies against fetal red blood cell antigens can cross the placenta and enter the fetal circulation. This may cause hemolytic disease of the fetus and newborn (HDFN), leading to fetal anemia, hydrops fetalis, and potentially intrauterine fetal death. Maternal antibodies include natural and allo-antibodies, the latter forming through sensitization from pregnancy, transfusion, or transplantation. Clinically, RhD incompatibility is most significant. In RhD-negative women, IgG anti-RhD antibodies may form after exposure to RhD-positive blood (e.g., from a prior pregnancy) and cross the placenta in subsequent pregnancies, causing HDFN. The risk is higher in multiparas. While anti-D immunoglobulin and intrauterine transfusion (IUT) are standard for prevention and treatment, plasma exchange may be used before IUT is feasible (<18–20 weeks) or if IUT is technically difficult [1–3].