If you are making the claim, then you have to prove it. YOu know that. SAying it is "logical" doesn't mean anythign at all in this case. Here is one reason why: Even granting your entire premise, you have to prove that a one time spike in cortisol acts hte same as long erm stress. And then you have to prove the spike is high enough to retard conception: all your cortisol info shows is that it effects miscarriage frequency AFTER conception.