to those wondering How someone without a uterus can have a period: it actually has very little to do with the organs!
Estrogen is a set of instructions that your body follows. when it's in constant supply at the right levels, your body will start picking out a schedule for when it needs to release a few other hormones, and start squeezing the ever-loving shit out of the MUSCLES that it expects to be around those organs.
Remember, bleeding is only a small part of a period. the main symptoms are muscle cramps, pain or discomfort in the lower abdominal area(because of the cramps), irregular bowel movements(because of the cramps), needing to pee more(because of the cramps), bloating, craving specific foods, nausea, and fluctuations in energy levels & nutritional needs. none of that requires a uterus or ovaries; even the bloating is only PARTIALLY from being full of blood.
this is also why cis women born without functioning reproductive systems(i.e. womb is just scar tissue, neither ovary actually works, developed a third kidney instead of a uterus, that kind of thing) can still have periods throughout their life. as long as they're producing lots of estrogen, it's gonna happen!