A combined oral contraceptive, or the pill, used continuously (without taking a week off to induce menstrual flow) is currently the best and safest choice for astronauts who prefer not to menstruate during missions, says Varsha Jain, a gynecologist and visiting professor at King's College London.

How does a period work in space?

Studies have shown that women can have periods as normally in space as they do on Earth. What's more, menstrual blood flow isn't actually affected by the weightlessness we experience in space, so it doesn't float back in – the body knows it needs to get rid of it.

How do female astronauts have periods?

Most women opt instead to use contraceptives and put their periods on hold, both in preparation for and during spaceflight, as highlighted in the paper by Jain and her colleagues. “NASA flight surgeons are finding female astronauts just don't want to have to deal with their periods,” Jain said.