Another point that could be made is that, unless the ability to have children has been surgically removed, perhaps because of cancer, people don't really "know" that they can't have children. At most, they've been told they can't, or they assume they can't (because they haven't) ... but the literature is full of situations of people who "couldn't have children" having them.
Whether these situations could be considered miraculous, or whether they simply illustrate the imperfection of medical knowledge, would be a case-by-case theological question :-).
Lesson 21: Holy Matrimony and Holy Orders BY FATHER ROBERT ALTIER BUMP
There are certainly women who have had hysterectomies. Nothing stops God if He wills it, but it does make the odds literally miraculous.