Scientists sent a menstrual cup to space. This is how it went

What can you do if you get your period in space? Scientists are making that question a little easier to answer by testing how well a menstrual cup, a popular reusable period product, holds up against the pressures of space flight.

In 2022, a research group called AstroCup placed two menstrual cups on an uncrewed rocket flight that lasted about 9 minutes after launch and hit an altitude of 1.9 miles (3 kilometers). This put the menstrual cups, made by the brand Lunette, at risk of vibration and other stressors that could damage their structure or affect how well they hold liquid. But leak tests using glycerol and water found that the menstrual cups held up with no damage, and that the material didn't degrade. The results of the study were published recently in NPJ Women's Health.

Menstrual cups are reusable, flexible silicone-based containers that someone can wear during their period to collect blood. They've grown in popularity in recent years as a more sustainable alternative to single-use period products, like tampons and pads, because a single one of these can be used for years. While most astronauts who are able to menstruate opt to temporarily put their cycle on hold through hormonal suppression (more on that below), humankind's continued exploration of space means women won't always be able to pause their cycles — or, they may simply not want to. What's more, recycling systems on spacecraft weren't traditionally designed to handle blood, and managing a period with single-use tampons can create more waste and hassle.

Taking all this into account, the AstroCup team see menstrual cups as a potential viable solution for future use and a big foot in the door for more gravity-defying health options in space. However, authors of the article pointed out that more research needs to be done on how menstrual cups fare in reduced gravity or on longer-term missions, when removal of the cup and its contents may be more affected. To gain more data, authors of the article hope to get different menstrual products on the International Space Station to compare and test for efficacy.

"Now we can start implementing and redefine health autonomy in space," astrobiologist Lígia Coelho, lead researcher of AstroCup, fellow at Cornell University's Carl Sagan Institute and lead author of the study, said in a statement.

Why astronauts pause their periods (and why that won't work forever)

Temporarily stopping your period by continuously taking birth control pills (i.e. skipping the seven-or-so placebo pills in a month-long pack) is seen as safe for many people to do on Earth, and it may even have benefits for women with certain reproductive health problems such as severe endometriosis or premenstrual dysphoric disorder (PMDD). There's no medical need to bleed every month when taking hormones that pause ovulation, which birth control pills do when they contain synthetic estrogen and progestin.

In space, this makes the life of an astronaut a bit easier by reducing the need to manage menstruation with menstrual products — and potentially even limiting side effects of natural hormonal fluctuations such as cramping or low energy levels. Other birth control hormonal methods that reduce the amount of blood lost during menstruation or stop it all together, such as intrauterine devices (IUDs), may also be options for astronauts, but research on how they fare in space is non-existent. On Earth, IUDs and implants (Nexplanon) that contain progestin only are also linked to more breakthrough bleeding, especially in the first year of use, which means that they won't eliminate the period product problem for all users.

But on Earth and in space, added estrogen can have side effects, like an increased risk of blood clotting, and a hormonal regiment won't be suitable for every person. Combined oral contraceptives also may have side effects related to bone density that need to be studied in space, as the authors noted in the new study.

And while reproduction and pregnancy in space is purely theoretical and years ahead of us as a species, effectively managing menstrual cycles in space will be crucial to reproducing outside Earth. More options will open more doors.

"More women will have the opportunity to go to space for even longer missions, and it is paramount that their autonomy on menstrual options is respected," authors of the NPJ article wrote.

"Astronauts on Moon and Mars missions may decide that they would like to keep menstruating for personal preference, as well as for health or reproductive reasons."

The study was published on Dec. 2 in the journal NPJ Women's Health.