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Irregular Menstrual Cycle

Many factors can lead to an irregular menstrual cycle.

Women who exercise intensively often experience irregular menstrual cycles. [©Shutterstock, 2010]
©Shutterstock, 2010
Women who exercise intensively often experience irregular menstrual cycles.

In order to understand what an irregular menstrual cycle, or period, is and how it affects women, it is first necessary to define a regular menstrual cycle. Both irregular and regular menstrual cycles may feature the same symptoms cramps, stomachache, headache, mood changes or unpredictable bleeding so how are they different?

The average menstrual cycle spans a period of 28 days, but the actual length of time varies for individual women, due to differences in womens hormone levels. A so-called regular period may occur anywhere from every 20 days to every 35 days. While a typical menstruating woman may bleed for five days, it is not unusual for her period to last from three days to one week. Signs of an Irregular Menstrual Cycle

According to the experts at Epigee, 30 percent of women at reproductive age experience irregular menstrual cycles. Although some signs of an irregular menstrual cycle, such as a late period, do not ordinarily lead to any serious medical problems, women may still feel concern. Different levels of bleeding may also cause worry, such as early bleeding, bleeding that occurs between cycles or heavy bleeding. Very light bleeding may cause unease when a regular flow is expected. On the other hand, periods that last beyond the normal span or that occur more than once during the month may also cause alarm.

There are many factors that may contribute to an irregular menstrual cycle, but the underlying cause is usually an imbalance of hormones, which can be easily remedied. In order to determine the specific cause of irregularity, it is advisable for women to first receive a complete physical exam. Given blood tests should include a thyroid function test and a complete blood count to rule out anemia. The physical should also include a pelvic exam to rule out the presence of any abnormalities, polyps or infection. If concern over an irregularly late or missed period coincides with a womans effort to become pregnant, the result of the physical exam could be good news.

Causes of an Irregular Menstrual Cycle

The hormones that regulate the menstrual cycle are estrogen and progesterone, which are produced in the pituitary gland and function in the hypothalamus and ovaries. Like many bodily functions, this internal regulatory process can be affected by a number of outside factors that may disrupt normal hormone levels. According to Epigee, these outside factors may be emotional or physical.

Some of the most common factors include:


When a woman feels stressed, her adrenal glands secrete the hormone cortisol, which may disrupt normal hormone function.


After a girl gets her first period, it may take several years for her hormone function and menstrual cycle to become regular.


Female athletes or women who exercise intensively often experience irregular menstrual cycles.


Crash diets, poor nutrition and obesity can disrupt hormone levels, and sufferers of anorexia or bulimia either seldom menstruate or have irregular cycles.


Use of hormonal birth control pills can introduce new hormone levels into the body, which may affect a womans menstrual cycle.


A pregnant womans body generates irregular hormone levels that interrupt the menstrual cycle.


Women over 35 may begin to experience the transitions in hormone levels that lead to menopause, during which a womens menstrual cycles eventually taper off.


Other factors that may cause irregular menstrual cycles include smoking, drug and alcohol abuse, caffeine, various medications, chemotherapy, childbirth, miscarriage and breastfeeding.

Menstruation and the Moon

An interesting corollary to the discussion of irregular menstrual cycles among Western women is an observation from nature by some scientists about how women in traditional societies ovulated and menstruated in synchronization with the lunar month. Noting that the term menses, another word for menstruation, is derived from the Greek word for moon, mene, and that the moon takes about 28 days to revolve around the Earth, scientists theorize that women in societies that lacked artificial light at night tended to ovulate at the time of the full moon and menstruate with the advent of the new moon.

According to The Weston A. Price Foundation, studies have found a correlation between the presence of artificial light at night and irregularities in the menstrual cycle. Another theory, presented by PLoS Clinical Trials is that exposure to bright natural light in the early morning tends to result in more regular menstrual cycles.

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