Definition

The normal monthly shedding of blood and tissue from the lining of the uterus (womb) when pregnancy does not occur. During a menstrual period, menstrual blood and tissue flow from the uterus through the cervix and pass out of the body through the vagina. A menstrual period usually occurs about every 28 days (except during pregnancy) and lasts 3 to 5 days, but this can vary from person to person. It normally starts during puberty and ends at menopause. Also called menses and menstruation.