A woman's first period is a sign that she has begun puberty. Every woman has a menstrual cycle, though the number of days in her cycle may vary. Menstruation occurs every month for a few days when the woman is not pregnant: the uterine lining breaks down from the absence of a fertilized egg, resulting in menstrual bleeding. However, some women can have problems with their period, such as pain, extra bleeding or lack of a period.
Starting
According to the National Institutes of Health, most women start their menstruation around the age of 12. After menstruation begins, menstrual bleeding will occur every month until the woman reaches menopause. According to the National Institutes of Health, menopause usually occurs at age 51.
Cycle Duration
According to the National Women's Health Information Center, the average menstrual cycle lasts for 28 days. However, the length of a woman's menstrual cycle is dependent on her age. During a woman's young teenage years, her menstrual cycle can last from 21 days to 45 days. When the woman enters her adult years, her menstrual cycle can range from 21 days to 35 days. Usually, menstrual bleeding lasts between three to five days.
Ovulation
Around day 14 of a woman's menstrual cycle, an egg leaves the woman's ovaries, a process called ovulation. According to the National Women's Health Information Center, the egg travels through the woman's fallopian tubes towards the uterus. During this time, there is a rise in the woman's hormones and the uterine lining is preparing for a pregnancy. If the woman does not become pregnant, the uterus sheds its lining.
Bleeding
After the uterus sheds its lining from the lack of a pregnancy, the bleeding part of a woman's menstrual cycle begins. According to the National Institutes of Health, menstrual blood is only part blood; the rest is tissue from inside the uterus. The menstrual blood flow starts in the uterus, flows through a small opening in the cervix and out through the vagina.
Cycle Problems
Some women, according to the National Women's Health Information Center, have problems with their menstrual cycles. One of the conditions, amenorrhea, is the absence of the woman's period. This includes women who have not started menstruation by the age of 15, or have not had a period for 90 days when they usually have regular periods. Some women suffer from post pill amenorrhea after they come off the birth control pill. Other women may have dysmenorrhea, which causes painful periods with severe cramps. Abnormal uterine bleeding can also occur in some women, which is different from regular menstrual bleeding.
