I would have to say that it will differ from person to person. Here's why I say that... the depo shot has the same hormone as the mirena but in a larger dose because it is only effective for the 3 months. I have been told a lot of women had difficulties getting pregnant when they went off the depo shot. Well, I had the depo shot and I have gotten pregnant 2x since going off of it. So, as far as the mirena, there may be women who can and some who can't I think for the most part it effects each of us differently in some areas and the same in others. I would definitely advise this... I would do a very thorough cleansing of all the hormones and toxins it placed in you before even trying and avoiding any other BC. Good luck to you.