Final answer:
Erythroblastosis fetalis, or hemolytic disease of the newborn (HDN), can occur when an Rh-negative mother develops antibodies against an Rh-positive fetus. The mother's immune system mounts an immune response during the first pregnancy, causing anemia in a subsequent Rh-positive pregnancy. Treatment with Rh factor antibodies can prevent this immune response.
Step-by-step explanation:
Erythroblastosis fetalis, also known as hemolytic disease of the newborn (HDN), can develop if an Rh-negative mother produces antibodies against an Rh-positive fetus. During the first pregnancy with an Rh-positive child, the mother's immune system mounts a primary antibody response to the fetal blood cells that enter her bloodstream. If the mother has a second Rh-positive child, the IgG antibodies against Rh-positive blood cross the placenta and attack the fetal blood, causing anemia. This condition is treated with antibodies specific for the Rh factor, given to the mother during the first and subsequent births to prevent the immune response.