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Menstruation 101

What to Know About Her Time of the Month

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Updated February 10, 2009

Whether you are a mom remembering the days when puberty hit or a dad who doesn't know what hit him, there are a few basics every parent should know about a teen's menstrual cycle.

What is Menstruation?

Menstruation is known by many names – menses, period, that time of the month or even “Aunt Flo.” During menstruation, the uterine lining that was building up throughout the month sheds. This shedding of the blood and tissue from the uterus through the vagina is menstruation.

Menstruation is just one part of a woman's menstrual cycle. The menstrual cycle is a series of hormonal and physical changes that prepare a woman's body for pregnancy. If pregnancy doesn't happen, the body resets itself to prepare for another attempt at becoming pregnant.

Too Early, Too Late or Just Right?

Timing is everything to parents. Did she get her period too early? It is a problem that she hasn't gotten it yet? In the United States, the average age of the first menstruation is 12 years old, but a girl can get her period anytime from the ages of eight to 15 years old.

What is a “Normal” Cycle?

A menstrual cycle is measured from the beginning of one menstrual period to the beginning of the next. The average menstrual cycle is about 28 days, but it can range between 21 to 45 days and still be a normal cycle. Menstrual bleeding typically lasts three to five days, although a range of two to seven days can be the norm for some women.

During the first few years after the first period, your teen's cycles may not be regular or predictable These early cycles are frequently anovulatory, meaning no ovulation occurs during the cycle. Although cycles usually become regular within 2 years of the first period (menarche), it can sometimes take from eight to 12 years after the first period to ovulate regularly. It would be impossible to predict which cycles would have ovulation or not, so it doesn't mean that teen girls in these early years are not fertile.

Phases of the Menstrual Cycle

The uterine lining, the ovum (or egg) and hormone levels are all changing and cycling throughout the entire monthly process. There are essentially four phases of the menstrual cycle: menstruation, the follicular phase, ovulation and the luteal phase.

  1. Menstruation. The uterine lining and blood sheds, signaling the beginning of the menstrual cycle. This phase varies in length from woman to woman, contributing to the differences in menstrual cycle length.
  2. The Follicular Phase. During this time, the ovaries are being stimulated to produce a mature egg and so they mature throughout this phase. Additionally, the uterine lining is growing, preparing for possible egg implantation if pregnancy would occur. The length of this phase also varies.
  3. Ovulation. The ovaries, by way of an ovarian follicle, release a mature egg after a surge of hormones that triggers the event.
  4. The Luteal Phase. This phase lasts a consistent length of time, an average of 14 days with a day or two variation. During this time, the uterine lining continues to grow, preparing for embryo implantation. The ovarian follicle becomes the “corpus luteum” -- the yellow body that produces hormones that would help to promote a pregnancy if it occurs. If pregnancy doesn't occur, the cycle begins again with menstruation.

When to Worry

From the U. S. Department of Health and Human Services, you should see your pediatrician or family practice provider if:

  • Your daughter hasn't gotten her period by the time she is 15 years old, she hasn't gotten it by three years after breast growth or if breasts haven't started to grow by age 13.
  • Her period suddenly stops for more than three months.
  • Her period becomes irregular after they were regular and predictable
  • Her period occurs more often than 21 days or less often than 45 days.
  • Her period lasts more than seven days.
  • She is bleeding more heavily than usual or using more than one pad or tampon every one to two hours.
  • She is bleeding between periods.
  • She has severe pain during her periods.
  • She suddenly gets a fever or feels sick after using a tampon.

If there is ever a concern about your daughter and her menstrual cycle, talk to a trusted healthcare professional. Sometimes there are underlying hormonal issues or other concerns that your health care provider can address.

Sources:

Adolescent Health Care: A Practical Guide. Edited by Lawrence Neinstein. Lippincott, Williams & Wilkins, Philadelphia, PA, 2002

Menstruation and the Menstrual Cycle. National Institutes of Health, National Institute of Child Health and Human Development. September 6, 2008. http://www.nichd.nih.gov/health/topics/menstruation_and_the_menstrual_cycle.cfm

Menstruation and the Menstrual Cycle. U.S. Department of Health and Human Services, Office on Women's Health. September 6, 2008. http://www.womenshealth.gov/faq/menstru.htm

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