Red cell alloimmunization in pregnancy, a condition where maternal antibodies target fetal red blood cells, poses significant risks, including hemolytic disease of the fetus and newborn (HDFN). This chapter explores the mechanisms, clinical implications, and management strategies for alloimmunization. It delves into the procedure of intrauterine transfusions (IUTs), detailing the factors influencing their timing and frequency, as well as associated complications and their impact on perinatal outcomes. Current and future therapeutic options for severe cases are discussed, highlighting innovative approaches such as targeted immunotherapy. The chapter emphasizes the importance of early detection, individualized management, and adherence to updated guidelines to optimize maternal and fetal health outcomes.