<prompt> The fetus which is paly foreign to the mother is not rejected by mother due to :Immunosuppressive effect of placental hormonesAbsence of HLA molecules in villous trophoblastProduction of blocking AntibodyAll of the above  <response>: Ans. is d i.e., All of the aboveThe fetus and the placenta contain paternally determined antigens which can lead to immunological rejection. The placenta has some role in preventing such a rejection:Placental hormones EPF,PAPP-A,STERIODS HCG have got some immunosuppressive effect.There is production of blocking antibodies by mother in response to TLX trophoblast lymphocyte cross reactive antigen which protect the fetus from rejection.Absence of HLA molecules in villous trophoblast. 