The first formal study of menstruation in space launches this year through a project called Operation Period, marking the first time researchers will systematically investigate how microgravity affects the menstrual cycle. Astronauts participating in missions to the International Space Station will document their menstrual experiences using a dedicated app, collecting data on cycle length, flow, symptoms, and any changes they experience during spaceflight.
The research addresses a long-standing gap in space medicine. When Sally Ride became the first American woman in space in 1983, NASA infamously asked whether 100 tampons would suffice for her one-week mission, reflecting the agency's lack of understanding about menstruation in weightlessness. Decades later, despite more than 70 women having flown to space, researchers have gathered only anecdotal reports about how spaceflight affects menstrual health.
Operation Period will collect data from female astronauts across multiple space agencies, including NASA, ESA, and Roscosmos. Participants will log information before, during, and after their missions, creating the first comprehensive dataset on this topic. The study examines whether microgravity alters hormone levels, cycle regularity, or menstrual flow. Researchers will also investigate potential connections between spaceflight stress, radiation exposure, and menstrual changes.
The project addresses practical concerns for long-duration missions. As space agencies plan extended stays on the Moon and eventual Mars missions, understanding menstrual health becomes essential for mission planning, astronaut health, and ensuring women can perform their duties without unnecessary complications or stigma.
Scientists emphasize that menstruation affects roughly half the potential astronaut population during their reproductive years. Ignoring this basic biology undermines mission success and astronaut wellbeing. The research will help NASA and other agencies develop better protocols for managing menstrual health in space, from appropriate