Rh alloimmunization, also known as Rh incompatibility, is a condition that occurs when a pregnant woman with Rh-negative blood type is exposed to Rh-positive blood from her fetus, leading to the production of antibodies against the Rh antigen. This immune response can cause hemolytic disease of the newborn (HDN), which may result in anemia, jaundice, and other complications in the affected baby.