This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
The fetus (which is paly foreign to the mother) is not rejected by mother due to : 
Select and explain. 
A. Immunosuppressive effect of placental hormones, B. Absence of HLA molecules in villous trophoblast, C. Production of blocking Antibody, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: 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.