<prompt> The consequences of Rh incompatibility are not serious during first pregnancy becauseAntibodies are not able to cross placentaAntibody titre is very low during primary responseIgG generated is ineffective against fetal red ceellNone  <response>: Initially in mother IgM antibodies are formed that does not cross placenta and subsequently during next exposure IgG antibody are formed which can cross placenta and hemolysis will occur. 