A study has confirmed that there is no evidence that period sex increases you risk of endometriosis. Nope, feel free to have at it any time of the month. Endometriosis is a disorder in which the tissue that normally lines only the inside of your uterus (the endometrium) grows outside of itaround the ovaries, bowel and other areas in your pelvis. The tissue grows thicker throughout your menstrual cycle, then breaks down and bleeds, just as it would inside your uterus. But because the blood and tissue have nowhere to go, that leads to (often intense) pain, irritation and eventually scar tissue.
While the exact cause of endometriosis is still unclear, theres no evidence that period sex increases your risk. (In fact, one study linked sex during menses to a decreased risk.) The myth may stem from traditional Chinese medicine theories that having sex during your period disturbs the natural downward flow of menstrual blood, pushing it back into the uterus.
Western medicine has a term for a real phenomenon that sounds similar but isnt caused by sex, nor is it the likely trigger of endometriosis: retrograde menstruation. Many experts think that all women experience some menstrual backup from time to time, usually without ill effects, but that women who develop endometriosis may have a hormonal or immune system problem that allows the tissue to become implanted.
