Final answer:
Hemolytic disease of the newborn (HDN) will not occur if the father is Rh-negative, as the Rh antigen is found on Rh-positive red blood cells. If the mother is Rh-negative and has been sensitized to the Rh antigen during a prior pregnancy, HDN may occur if the second fetus is Rh-positive.
Step-by-step explanation:
Hemolytic disease of the newborn (HDN) will not be possible if the father is Rh-. This is because the Rh antigen is found on Rh-positive red blood cells, and an Rh-negative person can usually carry an Rh-positive fetus without difficulty. However, if the mother is Rh-negative and has been sensitized to the Rh antigen during a prior pregnancy, HDN may occur if the second fetus is Rh-positive. During the first birth, fetal blood enters the mother's circulatory system, and anti-Rh antibodies are made. These antibodies can cross the placenta and attack the blood of the second fetus, causing anemia.