Women here on Earth may think of their periods as monthly inconveniences, but consider what it's like for astronauts aboard the International Space Station (ISS).
Up there, maintaining personal hygiene in general is not easy, as limited water is available for washing. The added challenges of changing hygiene products in microgravity only make things even more difficult.
Then there's the issue of plumbing: The water recycling system onboard the ISS — used for reclaiming water from urine — wasn't designed with the possibility in mind that there would be menstrual blood in the mix. [7 Everyday Things that Happen Strangely In Space]
Indeed, there are several reasons why an astronaut might want to opt out of getting her period in space. But what's the best way to go about it? For a short mission, an astronaut may simply choose to time her cycle around her stint in space by using birth control pills, but for longer missions, skipping periods entirely may be preferred, said a new review of the subject, published today (April 21) in the journal npj Microgravity.
Skipping periods (also known as "menstrual suppression") is becoming more common among women in general and is gaining acceptance by more and more doctors, said the review authors, Dr. Varsha Jain, a visiting researcher at the Centre of Human & Aerospace Physiological Sciences in London, and Dr. Virginia Wotring, an assistant professor at the Center for Space Medicine at Baylor College of Medicine in Texas.
Currently, there are several options for women who choose to skip their periods, but whether these options will fare as well during long spaceflights as they do here on Earth is the question, according to the review.
"With more women going into space, we need to ensure they have the most up-to-date information" on the options available to them, Jain said in a statement.
So what's an astronaut to do?
One of the most common ways for a woman to skip her period is by taking the pill, which uses a combination of estrogen and progesterone to suppress the menstrual cycle. While the authors of the review note that this method works well (in fact, it's long been used in spaceflight, they write) some questions do arise.
For example, taking hormones may affect bone density. While such slight losses in bone density are generally not a concern here on Earth, during spaceflight, where bone-density loss is accelerated, this would be more problematic, the authors said. [Birth Control Quiz: Test Your Contraception Knowledge]
And of course, taking the pill each day requires, well, a pill for each day. As audiences learned watching the movie "The Martian," every extra bit of weight counts on a spaceflight. The review's authors estimate that a three-year mission would require about 1,100 pills, plus their packaging. The authors also note that the stability of these drugs over such a long time in space has not been tested.
So rather than the pill, long-acting reversible contraceptives, or LARCs, may be an astronaut's best option, the authors wrote. These contraceptives include intrauterine devices (IUDs) and under-the-skin implants.
Neither option has been shown to affect bone density in studies on Earth. In addition, a single IUD or under-the-skin implant would eliminate the extra bulk and stability issues of the pill, the authors wrote. And neither option would be expected to interfere with an astronaut's ability to perform her tasks on the mission, the researchers wrote.
On a more squeamish note, the authors point out that there are no reports in the medical literature studying whether the devices could shift around in the body as a result of the strong gravitational forces that an astronaut experiences during launch or landing.
Currently, two types of IUDs are available. One type, which releases small amounts of hormones into the body over time to suppress a woman's menstrual cycle, is the preferred option for spaceflight. The other available IUD prevents pregnancy by releasing copper ions, but it does not suppress a woman's period.
Subdermal implants work in a similar way as the hormonal IUD; they release small amounts of hormones over time. Unlike IUDs, however, which are inserted into the uterus, the subdermal implant is inserted just beneath a woman's skin, typically in the upper arm. The implant doesn't usually interfere with a woman's clothing on Earth, and it's unlikely that the method would cause problems in specific spacesuits, the review said.
Because both options take time to effectively suppress a woman's period, the authors said that an astronaut who chooses a LARC should have it inserted at least 1.5 to 2 years before her mission.