Menstruation 101
The basic facts of menstruation every woman should know

Menstruation, also called menses, menstrual period, or period, is a woman's monthly bleeding. When a woman has her period, she is menstruating. The menstrual blood is made up of blood and tissue that lines the uterus. It flows from the uterus through the cervix and through the vagina.
The menstrual cycle helps a woman's body prepare for the possibility of pregnancy each month. A cycle starts on the first day of a period, with the average menstrual cycle being 28 days long. However, a cycle can range anywhere from 23 days to 35 days.
The menstrual cycle involves the brain, pituitary gland, uterus and cervix, ovaries, fallopian tubes, and vagina. Hormones released by these parts rise and fall during the month and make the menstrual cycle happen.
During the menstrual cycle
During the start of the menstrual cycle, estrogen levels rise and make the lining of the uterus grow and thicken. An egg (ovum) in one of the ovaries starts to mature in response to hormones. Finally, the egg leaves the ovary and is released down the fallopian tube. This process is called ovulation.
The egg begins to travel through the fallopian tube to the uterus in the second half of the menstrual cycle. Then, progesterone levels rise, helping prepare the uterine lining for pregnancy. The woman becomes pregnant if the egg becomes fertilized by a sperm cell and attaches itself to the uterine wall. If the egg is not fertilized, it either dissolves or is absorbed into the body. Estrogen and progesterone levels drop, and the thickened lining of the uterus is shed during the menstrual period if pregnancy does not occur.
What is a typical menstrual period like?
A typical menstrual cycle starts when the thickened uterine lining and extra blood are shed through the vaginal canal. Always keep in mind that a woman's period may not be the same every month, and it may not be the same as other women's periods. Periods can be light, moderate, or heavy, and the length of the period also varies. Although most menstrual periods last from three to five days, anywhere from two to seven days is considered normal. Periods may be very irregular for the first few years after menstruation begins. Women approaching menopause might experience irregular cycles as well. To help with irregular periods or other problems with the menstrual cycle, sometimes birth control pills are prescribed.
Period symptoms
Women often experience cramps during their period. Other problems include pain, heavy bleeding, and skipped periods.
Normal age
In the United States, the average age of a girl starting menstruation is twelve. However, a girl may begin menstruating between the ages of 8 and 16.