I'm about to do a bit of what-if-ery, then go to bed. Bear with me (or ignore me).
If you were a person of either gender, living at any time before a couple of hundred years ago, you would find the fact of menstruation very weird. You have little idea of what happens inside the body and you believe that everything is the mysterious work of supernatural forces, even down to the monarch being personally chosen by your god/s. It is observed that women bleed a lot, every month, but don't die. You must, surely, think this is evidence of something supernatural about women?
Whether you think it's evidence of being especially gifted by the god/s, or of having powers originating from darker sources (which is probably determined by what your cultural leaders told you), it just can't seem rational to you. You've no idea about biological reasons for menstruation. Moreover, not all females bleed. They start when they become able to reproduce, and they stop when they're old. Therefore, this weirdness is specific only to women of childbearing age. Thus, 'logically', fertile women are superhuman.
I think that would lead to a degree of fear amongst those who could not bleed without dying - men, children and old women. I'm sure somebody's written a perceptive book on this, so would welcome a summary or a link to one!