Menstruation and the Menstrual Cycle

What is the menstrual cycle?

The menstrual cycle is the process by which a woman’s body gets ready for the chance of a pregnancy each month. The average menstrual cycle is 28 days from the start of one to the start of the next, but it can range from 21 days to 35 days. 

In the beginning of the menstrual cycle, levels of estrogen rise, causing the lining of the uterus to grow and get thicker.  An egg starts to mature in one of the ovaries.  Around the middle of the cycle, the egg leaves the ovary, a process called ovulation.

The egg begins to travel down the fallopian tubes to the uterus.  If the egg becomes fertilized by a sperm cell and attaches to the uterus, the woman becomes pregnant.  If not, the uterus does not need the extra thick lining and it begins to shed.

This shedding of the uterine lining through the vagina is menstruation.

What is menstruation?

Menstruation is the part of a woman’s monthly menstrual cycle in which blood and tissue are discharged from the vagina.  It is also commonly called a period or menstrual period.

Most menstrual periods last from three to five days.  In the United States, most girls start menstruating at age 12, but girls can start menstruating between the ages of 8 and 16.

What are the signs of menstruation?

Bleeding from the vagina is the primary sign of menstruation.

Some women have other symptoms around the time of menstruation, including:

  • Cramping, bloating, and sore breasts
  • Food cravings
  • Mood swings and irritability
  • Headache and fatigue

If these symptoms are severe, it might be a sign of premenstrual syndrome (PMS).  PMS usually occurs one or two weeks before menstruation.   PMS may affect a woman of any age who has menstrual periods. If the symptoms disrupt your lifestyle, you may want to seek medical care.

What if I have a problem with my menstrual periods?

A stop in menstrual periods (called amenorrhea), or other menstrual irregularites could be a sign that something is wrong. Menstrual irregularities can mean bleeding between your periods, skipping a period, or having very heavy menstrual periods. It is important to tell your health care provider about these symptoms.







Menstrual Problems

A variety of menstrual problems can affect girls. Some of the more common conditions are:

Dysmenorrheal                                                                                                                      menorrhagia           


What is dysmenorrhea?

Dysmenorrhea is a menstrual condition characterized by severe and frequent menstrual cramps and pain associated with menstruation. Dysmenorrhea may be classified as primary or secondary.

  • primary dysmenorrhea - from the beginning and usually lifelong; severe and frequent menstrual cramping caused by severe and abnormal uterine contractions.

  • secondary dysmenorrhea - due to some physical cause and usually of later onset; painful menstrual periods caused by another medical condition present in the body (i.e., pelvic inflammatory disease, endometriosis).

What causes dysmenorrhea?

The cause of dysmenorrhea depends on whether the condition is primary or secondary. In general, females with primary dysmenorrhea experience abnormal uterine contractions as a result of a chemical imbalance in the body (particularly prostaglandin and arachidonic acid - both chemicals which control the contractions of the uterus). Secondary dysmenorrhea is caused by other medical conditions, most often endometriosis (a condition in which tissue that looks and acts like endometrial tissue becomes implanted outside the uterus, usually on other reproductive organs inside the pelvis or in the abdominal cavity - often resulting in internal bleeding, infection, and pelvic pain). Other possible causes of secondary dysmenorrhea include the following:

  • pelvic inflammatory disease (PID)

  • uterine fibroids

  • abnormal pregnancy (i.e., miscarriage, ectopic)

  • infection, tumors, or polyps in the pelvic cavity

Who is at risk for dysmenorrhea?

While any female can develop dysmenorrhea, the following females may be at an increased risk for the condition:

  • females who smoke

  • females who drink alcohol during menses (alcohol tends to prolong menstrual pain)

  • females who are overweight

  • females who started menstruating before the age of 11

Consult your physician for more information.

What are the symptoms of dysmenorrhea?

The following are the most common symptoms ofdysmenorrhea. However, each adolescent may experience symptoms differently. Symptoms may include:

  • cramping in the lower abdomen

  • pain in the lower abdomen

  • low back pain

  • pain radiating down the legs

  • nausea

  • vomiting

  • diarrhea

  • fatigue

  • weakness

  • fainting

  • headaches

The symptoms of dysmenorrhea may resemble other conditions or medical problems. Always consult your physician for a diagnosis.

How is dysmenorrhea diagnosed?

Diagnosis begins with a gynecologist evaluating a female's medical history and a complete physical examination including a pelvic examination. A diagnosis of dysmenorrhea can only be certain when the physician rules out other menstrual disorders, medical conditions, or medications that may be causing or aggravating the condition.  


What is menorrhagia?

Menorrhagia refers to excessive bleeding during menstruation and is experienced by many women at some point in their lives.  Bleeding may be very heavy during a normal length period or in the form of prolonged bleeding every cycle. The average menstrual period lasts between four and five days and produces 60 to 250 ml of blood. What is “normal” varies quite widely between different women and one woman may be used to a regular 28 day cycle with a 3-day bleed while another may menstruate every 35 days for 7 days. Both may be considered normal.

Bleeding in excess of what is considered “normal”, acceptable to the individual or even healthy may be known as menorrhagia.

Menorrhagia can include:

  • Menstrual bleeding that lasts longer than seven days
  • Bleeding which soaks one or more sanitary pads or tampons every hour for several consecutive hours

  • Needing to use “double” sanitary protection or change sanitary pads or tampons during the night

  • Menstrual flow that includes large blood clots

  • Heavy periods that interfere with your regular lifestyle

  • Tiredness, fatigue or shortness of breath due to anemia

What causes heavy periods?

In a large proportion of women who experience excessive menstrual bleeding the cause is not known. There are certain conditions that may be to blame though. These may include hormonal imbalances, fibroids, uterine cysts and polyps, some forms of cancer and certain medications. Intrauterine contraceptive devices (IUD’s) may also lead to excessive bleeding.

In order to exclude the above causes, it is important to consult your health care provider about any changes in your menstrual cycle such as increased length of menstruation and heavier flow.  Any vaginal bleeding after menopause should also lead you to seek medical advice.

In young women who have begun menstruating in the last 18 months, menorrhagia is common due to irregular ovulation. Also, for women approaching the menopause, hormonal imbalance may contribute to heavier and irregular menstruation.

What complications can heavy periods cause?

Menstrual bleeding that is prolonged or excessive over several cycles may lead to health complications if not properly managed.  Iron deficiency anemia is caused by the loss of red blood cells during heavy menstrual bleeding. Anemia typically causes weakness and fatigue though women with more severe cases may even find themselves short of breath, light-headed, experiencing restless leg syndrome or a rapid heart rate. Anemia can be easily remedied and reversed with iron supplements and proper treatment of menorrhagia.

Menorrhagia is also associated with severe cramps and “period pains” as well as decreased fertility.



Medical dictionaries define oligomenorrhea as infrequent or very light menstruation. But physicians typically apply a narrower definition, restricting the diagnosis of oligomenorrhea to women whose periods were regularly established before they developed problems with infrequent flow. With oligomenorrhea, menstrual periods occur at intervals of greater than 35 days, with only four to nine periods in a year.


True oligomenorrhea can not occur until menstrual periods have been established. In the United States, 97.5% of women have begun normal menstrual cycles by age 16. The complete absence of menstruation, whether menstrual periods never start or whether they stop after having been established, is called amenorrhea. Oligomenorrhea can become amenorrhea if menstruation stops for six months or more.

It is quite common for women at the beginning and end of their reproductive lives to miss or have irregular periods. This is normal and is usually the result of imperfect coordination between the hypothalamus, the pituitary gland, and the ovaries. For no apparent reason, a few women menstruate (with ovulation occurring) on a regular schedule as infrequently as once every two months. For them that schedule is normal and not a cause for concern.

Women with polycystic ovary syndrome (PCOS) are also likely to suffer from oligomenorrhea. PCOS is a condition in which the ovaries become filled with small cysts. Women with PCOS show menstrual irregularities that range from oligomenorrhea and amenorrhea on the one hand to very heavy, irregular periods on the other. The condition affects about 6% of premenopausal women and is related to excess androgen production.

Other physical and emotional factors also cause a woman to miss periods. These include:

  • emotional stress

  • chronic illness

  • poor nutrition

  • eating disorders such as anorexia nervosa

  • excessive exercise

  • estrogen-secreting tumors

  • illicit use of anabolic steriod drugs to enhance athletic performance

Serious ballet dancers, gymnasts, and ice skaters are especially at risk because they combine heavy activity with a diet intended to keep their weight down. One study at the University of California San Francisco found that 11% of female ultramarathon runners had amenorrhea or oligomenorrhea. This is a much higher rate than in the general population. Women's coaches are becoming more aware of the problem and are encouraging female athletes to seek medical advice. A gynecologist is the doctor most experienced in diagnosing and treating oligomenorrhea.

Causes and symptoms

Symptoms of oligomenorrhea include:

  • menstrual periods at intervals of more than 35 days

  • irregular menstrual periods with unpredictable flow

  • some women with oligomenorrhea may have difficulty conceiving

Oligomenorrhea that occurs in adolescents is often caused by immaturity or lack of synchronization between the hypothalamus, pituitary gland, and ovaries. The hypothalamus is part of the brain that controls body temperature, cellular metabolism, and basic functions such as eating, sleeping, and reproduction. It secretes hormones that regulate the pituitary gland.

The pituitary gland is then stimulated to produce hormones that affect growth and reproduction. At the beginning and end of a woman's reproductive life, some of these hormone messages may not be synchronized, causing menstrual irregularities.

In PCOS, oligomenorrhea is probably caused by inappropriate levels of both female and male hormones. Male hormones are produced in small quantities by all women, but in women with PCOS, levels of male hormone (androgens) are slightly higher than in other women.

In athletes, models, actresses, dancers, and women with anorexia nervosa, oligomenorrhea occurs because the ratio of body fat to weight drops too low.


What is amenorrhea?

Amenorrhea is a menstrual condition characterized by absent menstrual periods for more than three monthly menstrual cycles. Amenorrhea may be classified as primary or secondary.

  • primary amenorrhea - from the beginning and usually lifelong; menstruation never begins at puberty.

  • secondary amenorrhea - due to some physical cause and usually of later onset; a condition in which menstrual periods which were at one time normal and regular become increasing abnormal and irregular or absent.

What causes amenorrhea?

There are several possible causes of amenorrhea, including the following:

  • pregnancy
    Females no longer ovulate when they are pregnant, thus, menstruation ceases temporarily.

  • ovulation abnormality
    Ovulation abnormalities are usually the cause of very irregular or frequently missed menstrual periods.

  • birth defect, anatomical abnormality, or other medical condition
    If a young woman has not started to menstruate by the age of 16, a birth defect, anatomical abnormality, or other medical condition may be suspected.

  • eating disorder
    Females with anorexia nervosa (or simply anorexia) and/or bulimia nervosa (or simply bulimia) often experience amenorrhea as a result of maintaining a body weight that would be too low to sustain a pregnancy. As a result, as a form of protection for the body, the reproductive system "shuts down" because it is severely malnourished.

  • over-exercise or strenuous exercise
    Many young female athletes in training experience absent menstrual cycles due to low body fat content.

  • thyroid disorder
    In many cases, an underactive thyroid gland (a condition called hypothyroidism in which the thyroid gland is producing insufficient amounts of the thyroid hormone) or an overactive thyroid gland (a condition called hyperthyroidism in which the thyroid gland secretes too much thyroid hormone - resulting in too much thyroid hormone in the bloodstream and overactivity of the body's metabolism) is responsible for the absent menstrual cycles.

  • obesity
    Females who are obese often experience amenorrhea as a result of excess fat cells interfering with the process of ovulation.

How is amenorrhea diagnosed?

Diagnosis begins with a gynecologist evaluating a female's medical history and a complete physical examination including a pelvic examination. A diagnosis of amenorrhea can only be certain when the physician rules out other menstrual disorders, medical conditions, or medications that may be causing or aggravating the condition. In addition, a diagnosis of amenorrhea requires that a female has missed at least three consecutive menstrual cycles, without being pregnant. Young women who have not had their first menstrual period by the age of 16 should be evaluated promptly, as making an early diagnosis and starting treatment as soon as possible is very important.