Regarding the second question, anti-B antibodies from a type-A mother rarely affect the RBCs of a type-B fetus because of the way antibodies work in the immune system. Type-A blood contains anti-B antibodies, but these antibodies are typically of the IgM class, which cannot cross the placenta. IgM antibodies are large and unable to pass through the placental barrier, thus posing little to no risk to the fetus (Kumpf & Almazan, 2020). However, the anti-D antibodies of an Rh-negative woman, which are usually of the IgG class, can cross the placenta. IgG antibodies are small enough to pass through the placental membrane, allowing them to bind to Rh-positive fetal red blood cells and cause hemolysis. This results in hemolytic disease of the newborn (HDN) when the fetus has Rh-positive blood (Weiner et al., 2019).