most body processes have muscles driveing them, and so work in space.
to my knowlage a woman’s period involves some level of muscle contraction, but is largely a matter of cells and blood just dislodgeing and falling out the ahem convenient drain at the bottom. what happens to women in space? for that matter what would happen with a woman standing on her head perminently? is this an issue? do infection rates skyrocket? ect?
After some massively TMI Googling, it appears that menstruation in space functions pretty much as normal, although there’s been no long-term female space station residents on whom to study the effect on menstrual cycles over time.
http://www.chron.com/content/interactive/space/missions/sts-093/stories/mission/990725b.html mentions the non-issue of dealing with it - just a matter of adding tampons to the shuttle supplies.
what is the longest a woman has been in space? have they ever actually done studys on periods in space? I mean, if it doesn’t all “come out” its doubtful the woman would simply fall over dead, and some would be bound to find its way out just moveing around.
is it something that works in general? by what mechnism? or just that so far no one really has complained and no one has gotten real ill?
As far as I can find, the longest is 14 days, by Shannon Lucid. This isn’t long enough to study menstruation in any relevant way. No doubt when there’s a long-term female resident, there’ll be studies done. As for the mechanics of it, I doubt that there’s any problem with not everything ‘coming out’ - IANA doctor, but I doubt that’s the case in normal situations.
What about Cosmonaut Elena Kondakova?
I would imagine that would probably be enough time to study something like this --at the time she would have been in her late 30’s, so probably not in menopause. I couldn’t find any information pertinent to the topic at hand, though…
Well, in a related question, what happens to women who are incapacitated? A woman in a coma would have a similar problem. I always thought that the contractions of the uterus dislodge the blood cells from the uterus (or it certainly feels like that’s what they’re doing) and things just “drained” out from there. And that’s just part of the body’s natural cleansing system which happens whether or not you’re actually having your period.
Although, from personal experience, periods don’t stop at night, they’re just lessened. Standing up after a night’s rest, produces a temporary, heavy increase in flow. So maybe the periods would just take much longer.
They could just use that birth control regimen (no dummy pills) which prevents periods.
Problem solved.
The site linked above also lists her stay of 188 days on board Mir. That she was 53 years old at the time might complicate the issue somewhat.
Here is an excellent article all about the current state of knowledge and future research needs about female reproductive health (including menstruation) in space. And this one repeats the current view that there is no problem.
TMI I bet with all the gravitational variation, it would be easy to sit on your string. And that is not fun.
Great - now I hear the thread title being announced by the “Pigs in space” guy.
Periods.
In.
SPAAAAAAAaaaace!!
I don’t know about various astronauts, but I know I’d go on the pill and stay on it. Thinking about how messy a period can be with gravity, if stuff started floating…AAAAAAAAA!!!
I wish someone would tell my body that. 
The OP asked whether infections could be caused by the menstrual flow backing up. I know that in yoga, they make a very big deal about not doing inverted poses during your period for that very reason. It’s considered a really bad idea to give your menstrual flow the opportunity to flow in the wrong direction.