The Menstrual Cycle

What is the menstrual cycle?

The Gynecology Program at Boston Children's Hospital encourages mothers to talk to their daughters about the normal changes occurring in female body during puberty, including the new need for safe sexual practices. Menstruation, while confusing at first, is a process each girl will deal with every month of her reproductive life.

• Around age 12, sometimes earlier and sometimes later, a young girl's body begins monthly cycles that ready her body for future reproduction. Menstruation is one part of the cycle that involves the shedding of the uterine lining. Her body needs to do this to avoid the risk of cancer and to get ready for the next cycle.
• During each monthly cycle, the endometrium, or the lining of the uterus, prepares itself to nourish a fetus, as increased levels of the hormones estrogen and progesterone thicken the walls.
• If a sperm doesn't fertilize the egg, which descended the fallopian tubes during ovulation, the endometrium and the blood and mucus from the vagina (birth canal) and cervix (opening to the uterus) flows out of the body through the vagina for four to seven days. This process is also called menses or her "period."

What is ovulation?

• When a young woman reaches puberty, she begins to ovulate, a process that sparks the beginning of the menstrual cycle. During ovulation, a mature egg cell (ovum) is released by one of the two ovaries, which are packed with all the eggs she will ever have.
• If a sperm meets with this egg as it travels down the fallopian tube towards the uterus, pregnancy could take place. If the egg isn'tfertilized, hormonal processes trigger the uterus to expel its lining, the process called menstruation.
• An average menstrual cycle lasts 28 days, starting with the first day of her period and ending on the first day of her next period. Most women ovulate on day 14.
• During ovulation, some women experience minor discomfort in their lower abdomen or brief spotting, while many others never notice it.
• A woman is generally most fertile (able to become pregnant a few days before, during, and after ovulation. But that doesn't mean she shouldn't use protection during sexual activity at all times.

What can my daughter expect during her menstrual cycle?

• On average, menarche (her first period) occurs between the ages of 12 and 14, generally two years after her breasts start to develop and not long after the growth of pubic and underarm hair.
• Many girls experience uncomfortable symptoms a few days before a period, commonly called premenstrual syndrome or PMS. Cramping, fatigue and irritability are common symptoms.
• Many adolescents don't ovulate during the first few menstrual cycles, and this may lead to irregular or heavy bleeding. Your daughter should see her gynecologist if she experiences any troubling symptoms.
• The American College of Obstetricians and Gynecologists recommends that a young woman consult her physician if she hasn't started to menstruate by the age of 16, and/or if she has not begun to develop breast buds, pubic hair or underarm hair by the age of 13 or 14.
• The Center for Young Women's Health, part of the Gynecology Program, provides extensive and easy to access information for girls with questions about her menstrual cycle. The following guide may be helpful to her: Puberty and Your Menstrual Cycle: A Guide for Teens.