Menstruation is the shedding of blood and tissue from the lining of the uterus that occurs approximately once a month in people who have uteruses until they reach menopause. It is one phase of the menstrual cycle, which includes menstruation, the follicular phase, ovulation, and the luteal phase. Sometimes, menstruation is called menses, a menstrual period, or simply a period.

During menstruation, the blood and tissue that has built up over the course of a month in the uterus flows out through the cervix, and out of the body through the vagina. Usually, menstruation lasts between five to seven days, but a period that lasts at least three days is considered normal.

On average, people with uteruses begin to menstruate around age 12. Not everyone will begin their periods at the same time, and some people will start as early as 8 years old and as late as 16. Menstruation is triggered by changes in a person’s hormone levels. The pituitary gland in the brain signals the ovaries to make and release certain hormones throughout a person’s menstrual cycle, and menstruation occurs when their progesterone levels begin to fall.

Menstruation is an indication that pregnancy has not occurred. The lining of the uterus thickens throughout the month so that if an egg is fertilized by a sperm, it can implant into this lining. When pregnancy does not occur, the body must shed the thickened lining and begin the cycle again. This is why a person does not get their period while they are pregnant.

Eventually, people stop menstruating around age 51. Around this age, a person’s hormone levels change and they experience a drop in estrogen and a loss of ovarian function, which stops the menstrual cycle. When a person has not had a period for a full year, they are considered to be in menopause. 

Some individuals experience additional symptoms when they are on their period while others do not. Headaches, cramps due to the contractions of the uterus, mood changes, bloating, acne, and breast tenderness are all common symptoms of menstruation.

An irregular period may be caused by a number of factors, so if you have any issues with your period, it is a good idea to contact a health care provider. Some issues may include not starting your period before the age of 16, experiencing severe pain during periods, suddenly bleeding much more than usual, not having your period for three months or longer without being pregnant, and bleeding between periods.

References:

• Cleveland Clinic. (2022, December 9). Menstrual Cycle. https://my.clevelandclinic.org/health/articles/10132-menstrual-cycle
  
  
• Planned Parenthood. (2023). https://www.plannedparenthood.org/learn/health-and-wellness/menstruation