Menstruation (pronounced men-stroo-EY-shuhn) is normal vaginal bleeding that occurs as part of a woman's monthly menstrual cycle. Menstruation occurs between menarche (pronounced muh-NAHR-kee), a girl's first period, and menopause.1 Menstrual blood flows from the uterus and passes out of the body through the vagina. In young females, the average menstruation time is 7 days or less.2 In the United States, most girls start menstruating between the ages of 11 and 14.2
Menstruation is one part of the menstrual cycle, in which female hormones prepare the uterus to support a pregnancy. The average menstrual cycle is 28 days. In young females it can range from 21 to 45 days.2 The menstrual cycle begins with the rise of estrogen levels, which causes the lining of the uterus to get thicker. Additionally, an egg starts to mature in one of the ovaries. Around the middle of the menstrual cycle, the egg leaves the ovary. This process is called ovulation (pronounced ov-yoo-LEY-shuhn). The egg travels down the fallopian tubes to the uterus. If the egg becomes fertilized by a sperm cell, it attaches to the uterus and results in pregnancy. If a pregnancy does not occur, the lining of the uterus is shed during menstruation.
- Sweet, M. G., Schmidt-Dalton, T. A., Weiss, P. M., & Madsen, K. P. (2012). Evaluation and management of abnormal uterine bleeding in premenopausal women. American Family Physician, 85, 35-43. [top]
- American College of Obstetricians and Gynecologists (ACOG) Committee on Adolescent Health Care. (2006). ACOG Committee Opinion No. 349. Menstruation in girls and adolescents: Using the menstrual cycle as a vital sign. Obstetrics & Gynecology, 108, 1323-1328. [top]