Menstruation is the periodic discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. This cyclic discharge is seen in females of certain mammalian species (including humans). It begins with the onset of menarche at or before sexual maturity and stops at or near menopause (the end of a woman’s fertility). The periodicity of menstruation gives rise to commonly used euphemisms such as “period” and “monthly”. Women typically stop menstruating if they conceive or if they are breastfeeding. When menstruation stops for longer than about 90 days in the absence of pregnancy or breastfeeding, a medical evaluation should occur, as a number of health problems can result in absent menstruation. Menstruation lasts from puberty until menopause among non-pregnant women.