[lyner]

Come to that, why don't bedridden women on Earth experience backflow?

There is a constant flow 'downwards' due to the cillia in the Fallopian tubes, I understand.  The tubes are pretty narrow and the fluids are pretty viscous so any flow rate would be slow. 0g (laying down) would not be likely to produce backflow. What about all the animals whose bodies are pretty much horizontal all the time? Evolution must have  sorted this out.
I imagine that hanging upside down in 1g conditions for some time might possibly cause problems. How do female trapeze artist figure in the statistics of Endometriosis? (What about bats?)

[Nizzle]

The answer is Peristalsis, which also occurs in fallopian tubes

[DrChemistry]

Will the astronaut's gas cloud ever collapse on itself and provide us with a second moon?

Unlikely. But imagine if it did happen. What would then happen to tides and seasons?

I also wonder where the excrements of the Astronauts go while they are out on a space walk. Surely they do not have time to get forth and back.  []