system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How would menstruation work in zero G?

Would it all just stay inside or proceed normally?
gpt
This was actually something that NASA scientists were worried about.  It was theorized that the blood might actually flow backwards causing something called retrograde menstruation.  In reality, it works basically the same way it does on earth.  Female astronauts use pads or tampons.