Asked by: Harriet Wulff, Ireland
Microgravity, such as that experienced on the International Space Station, has no effect on the menstrual cycle. In the 1960s, some experts warned against sending women into space over fears that menstruation and PMS could affect their ability to work. There were also concerns that blood might flow back into the body, pooling in the abdomen and causing peritonitis. The fears were unfounded.
However, the issue of storing sanitary items, together with limited washing water, means that women in space tend to take oral contraceptive pills to prevent menstruation during their mission.