Question: My 13 year old daughter was at the third Christmas lecture. Talking about it back at home, she wondered what happens to a woman's menstrual cycle in space, and looking a long time ahead, how would changes in bone density affect the ability to carry and give birth to a child?

Delma Childers answered on 4 Jan 2016:

There isn’t a lot available in scientific literature about these topics, but everything I read points to the cycle being pretty normal in space. There were concerns early on in spaceflight that without gravity, blood would flow backward into the fallopian tubes and abdomen and cause serious health problems, but those fears have never been confirmed. The other information I’ve found is that there is access onboard ISS to typical feminine hygiene products for female astronauts. Fun fact, here’s a real excerpt from an interview conducted with the 1st American female astronaut, Sally Ride:
“I remember the engineers trying to decide how many tampons should fly on a one-week flight; they asked, ‘Is 100 the right number?’
“No. That would not be the right number.”

Now, for the second part, there have been some studies with pregnant rats who were sent to space during their pregnancy and brought back to Earth for delivery. It wasn’t loss of bone density so much as loss of muscle that really prolonged labour for mothers who spent time in space. The pups fared much better than their mothers – space didn’t seem to significantly affect their development. This evidence suggests that giving birth to a child in space would be quite difficult, long and taxing for human mothers compared to deliveries on Earth.