I feel like you’re a man who doesn’t really understand what a period is, or what female anatomy really is. But I’ll simplify it.
A period is the shedding of the uterine lining after a fertilized egg fails to embed itself in it. So in order to get all of the lining out, the uterus needs to contract to push all of it out. That’s an over simplified way of putting it, but that’s essentially what happens.
It’s governed by hormones and genetics, and some women have it worse than others, and it tends to be worse during different parts of the cycle.
To answer your question about why it’s normalized, it’s because, to put it bluntly, women’s pain is ignored and dismissed. Women’s health in general is neglected.
Women who complain of pain to their providers are generally ignored, and not offered any kind of pain relief. It doesn’t matter what kind of pain it is, including childbirth (I can attest to being told my pain “wasn’t that bad” in the middle of labor). I had to fight for pain relief afterward, despite a third degree tear.
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