Hemolytic disease of the newborn

Hemolytic disease of the newborn (HDN), hemolytic disease of the fetus and newborn (HDFN) or erythroblastosis fetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta. Among these antibodies are some which attack antigens on the red blood cells in the fetal circulation, breaking down and destroying the cells.

Source: Wikipedia — Hemolytic disease of the newborn (CC BY-SA 4.0)