Menstruation is the time during a woman's natural cycle when bleeding occurs from the vagina. Menstruation usually lasts between three and seven days.

What is going on in the body?

Menstruation occurs when one of the eggs in the ovaries is released. The egg travels down the fallopian tube towards the uterus. Once the egg is released, estrogen encourages the uterus to build up a thick lining to prepare for pregnancy. If sperm from a male fertilizes the egg, the egg implants itself into the uterine wall and begins to grow a fetus.

If pregnancy does not occur, the uterus sloughs off the lining and excretes it through the cervix, or opening of the mouth of the uterus. This excreted uterine lining is the menstrual flow. This cycle is repeated about every 28 days. The amount of time between menstruation may vary from woman to woman and month to month. Any duration between periods from 19 to 35 days is considered normal.

What are the causes and risks of the condition?

The cause of menstruation is the natural maturation of the female body. A female becomes ready to menstruate as young as 9 or 10 years old. Most will start to menstruate by the time they are fifteen. Women can have problems if hormones are thrown off balance. Irregular or missed periods may be caused by stress, changes in weight, diet, or illness.