Menstrual Blood Girls, Your period might be light or heavy, painful or pain-free, long or short and still be considered typical. Mar 21, 2026 · The menstrual cycle has four phases: menstruation, the follicular phase, ovulation, and the luteal phase. Throughout the month, your hormone levels change depending on what menstrual phase you’re in. Learn more. In adult women, the menstrual cycle lasts anywhere from 21 to 40 days. NICHD is one of many federal agencies and NIH Institutes working to understand menstrual problems. Menstruation — aka having your period — is when blood and tissue from your uterus comes out of your vagina. As the uterus sheds its lining, vaginal bleeding follows. NICHD supports and conducts research on what causes menstrual irregularities and how best to treat and detect them. 34–2. vtv, 42, xol, 8zqjrm, xur, fsr7, wdljha, 9xdol, aywk, 3mmct0,