An Rh+ fetus carried by an Rh- mother?

Question

An Rh+ fetus carried by an Rh- mother may have agglutination within the blood. However a fetus with B blood carried by a mother with A blood will not have agglutination. Based on the knowledge of the immune system explain why.

Answer 1

A women's first pregnancy usually results in the delivery of a healthy baby. But, when bleeding occurs as the placenta detaches from the uterus, the mother may be sensitized by her baby's Rh+ antigens that pass into her blood stream. If so, she will form anti-Rh antibodies unless treating with RhoGAM before or shortly after she has given birth. RhoGAM is a serum containing anti-RH agglutinins. Because it agglutinates the Rh factor, it blocks the mother's immune response and presents her sensitization. If the mother is not treated and becomes pregnant again with an Rh+ baby, her antibodies will Cross through the placenta and destroy the baby's red blood cells, leading to erythroblastosis fetalis.

Answer 2

in a b baby with an a mommy, the fetal and maternal blood is  normally kept separate across the placenta. but if the fetus doesnt carry the antibodies for the rh+ mom, it can pretty much reject the baby and eventually abort it