Menstruation

Definition

Menstruation refers to the monthly discharge through the vagina of the blood and tissues that were laid down in the uterus in preparation for pregnancy .

Description

The cyclic production of hormones that culminates in the release of a mature egg (ovum) is called the menstrual cycle, which begins during puberty and ends at menopause . The first menstrual cycle is called menarche.

Hormones that control the menstrual cycle are produced by the hypothalamus, pituitary gland, and ovaries. The beginning of a menstrual cycle is marked by the maturation of an egg in an ovary and preparation of the uterus (womb) to establish pregnancy. Menstruation occurs when pregnancy has not been achieved.

The menstrual cycle is divided into four phases and is, on average, 28 days long (21–45 days). The onset of menstruation, called a period, monthly, menses, or menstrual period, begins a new menstrual cycle and is considered day one. This first phase usually lasts five days. Menstruation occurs in response to drops in the level of the hormone progesterone. It is estimated that a woman will have 500 menstrual periods in her lifetime.

The second phase of the menstrual cycle is called the follicular or proliferative phase. The ovary, in response to increasing levels of follicle stimulating hormone, begins the egg maturation process. Although 10–20 eggs begin to develop within follicles of the ovaries, usually only one egg reaches maturity. Follicles are clusters of cells that encase a developing egg, hence the name "follicular phase." Developing follicles release the hormone estrogen that stimulates the lining of the uterus, called the endometrium, to grow (proliferate) in preparation to receive an embryo (an egg that has been fertilized and begun dividing) and establish pregnancy. This is why the second phase is also called the "proliferative phase." This phase usually lasts through day 13.

The ovulation phase occurs in response to a surge in luteinizing hormone and is marked by the release of a mature egg from the follicle. Ovulation usually occurs on day 14.

The fourth phase is called the luteal, secretory, premenstrual, or postovulatory phase, and usually lasts from days 15–28. During this phase, the empty follicle, now called the corpus luteum, releases the hormone progesterone which further prepares the uterus for implantation of an embryo. The endometrium thickens because of cell growth, changes in blood vessels and glands, and increases in fluid. If pregnancy does not occur, the fall in progesterone levels initiates the onset of a new menstrual cycle. However, if pregnancy does occur, progesterone levels remain high and the endometrium is not shed.

In the United States, menstruation typically begins at 12.8 years of age in Caucasian girls and 12.4 years of age for African American girls. Factors that help to dictate the age at which menarche occurs include race, mother's age at menarche, nutritional status, body fat, as well as climate and elevation. Studies have shown that a body fat level of 17% is necessary for menstruation to begin.

Women who live together or work in close proximity tend to find that their cycles begin to coincide. During the menstrual cycle, the body releases hormones called pheromones, which may signal surrounding women's cycles to begin.

Puberty signals the maturation of a young woman's reproductive hormones. As a girl reaches puberty, the pituitary gland in the brain starts to produce the hormones that signal the ovaries to begin functioning. The interaction between these hormones and the hormones estrogen and progesterone causes the lining of the uterus to swell and thicken in anticipation of a fertilized egg. If the egg is not fertilized, the lining is discharged through the vagina, resulting in menstrual bleeding.

Menstrual problems

Women may experience menstrual cycles that fall outside of the norm as described above. Menstrual problems include missing a period, change in the length of the cycle, changes in the flow, color, or consistency of menstrual blood, and extreme pain or other menstrual symptoms.

Women may also experience emotional distress or wide mood swings during the luteal phase of the menstrual cycle. The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-IV, lists premenstrual dysphoric disorder (PMDD) in an appendix of criteria sets for further study. To meet full criteria for PMDD, a patient must have at least five out of 11 emotional or physical symptoms during the week preceding the menses for most menstrual cycles over the previous 12 months. Although the DSM-IV definition of PMDD as a mental disorder is controversial because of fear that it could be used to justify prejudice or job discrimination against women, there is evidence that a significant proportion of premenopausal women suffer emotional distress or impairment in job functioning in the week before their menstrual period. One group of researchers estimates that 3–8% of women of childbearing age meet the strict DSM-IV criteria for PMDD, with another 13–18% having symptoms severe enough to interfere with their normal activities.

Causes & symptoms

Menstruation is not an illness, but a normal part of the menstrual cycle. However, menstrual problems do occur, and are due to varying causes.

Amenorrhea

Amenorrhea is the absence of menstruation, and can be either primary or secondary. Primary amenorrhea is failure to menstruate by age 16 years in girls who have normal puberty, by age 14 years in those with delayed puberty, or two years after sexual maturation has occurred. Primary amenorrhea may be caused by genetic disorders, hormonal imbalance, brain defects, or physical abnormality of the reproductive organs. In 2003, a group of researchers reported on a new genetic mutation associated with primary amenorrhea. In addition, certain systemic diseases may delay puberty and menstruation. Delayed menstruation may occur in athletes, especially gymnasts, ballerinas, and long-distance runners because of insufficient body fat. Amenorrhea associated with athletic training and professional dance is a growing health concern, however, because it often occurs together with eating disorders and a loss of bone mass that can lead to early osteoporosis .

Secondary amenorrhea refers to the absence of menstruation after an interval of normal menstruation. It is identified as not menstruating for three months in females with irregular menstrual cycles, six months in females with normal menstrual cycles, and 18 months in females who had just started menstruating. Secondary amenorrhea can be caused by pregnancy, weight loss, excessive exercise , breast feeding, disease, or menopause. Menopause takes place when the ovaries stop producing estrogen, causing periods to become irregular and then stop. It generally occurs when a woman is between 48 and 52 years of age.

Dysfunctional and abnormal uterine bleeding

Dysfunctional uterine bleeding is excessive or irregular bleeding from the uterus. It is caused by uncontrolled estrogen production that leads to excessive build up of the endometrium.

Abnormal uterine bleeding is excessive bleeding during menstruation, frequent bleeding, and/or irregular bleeding. Abnormal bleeding can be caused by fibroids (noncancerous uterine growths), endometriosis (when endometrium spreads outside of the uterus), uterine infections, hypothyroidism , clotting problems, intrauterine devices (IUD), or cancer .

Dysmenorrhea

Dysmenorrhea is painful and difficult menstruation. Studies have found that 60–92% of adolescents suffer from dysmenorrhea. It usually begins six to 12 months following menarche. Symptoms may be severe enough to miss work or school, and prevent participation in normal activities. Risk factors for developing dysmenorrhea may include long menstrual periods, obesity , early age at menarche, smoking , and alcohol use.

Primary dysmenorrhea is believed to be caused by high levels of prostaglandins (fatty acids that stimulate muscle contractions, among other activities) which cause painful uterine muscle spasms. Symptoms of primary dysmenorrhea occur when bleeding starts and may include moderate to severe menstrual pain (crampy, spasmodic, and labor-like or a dull ache), nausea, vomiting, headache, fatigue, low back pain , thigh pain, and diarrhea .

Secondary dysmenorrhea is caused by conditions such as endometriosis, abnormalities of the pelvic organs, pelvic inflammatory disease , fibroids, ovarian cysts , tumors, inflammatory bowel disease , and salpingitis (inflammation of the fallopian tube). Symptoms of secondary dysmenorrhea usually occur a few days before bleeding starts. The symptoms depend upon the specific cause of dysmenorrhea, but pain is the hallmark symptom.

Heavy periods

Many women experience heavy menstrual bleeding during their periods, called menorrhagia. Heavy periods cause more blood loss than normal periods or may last longer than seven days. Women suffering from menorrhagia may lose up to 92% of their total fluid and tissue in the first three days of their cycle. Heavy menstruation is common in young girls who have just started their periods.

Menorrhagia is often caused by a failure to ovulate, which leads to a deficiency of progesterone. Without progesterone, the uterine lining becomes unstable and periods tend to be longer and unpredictable. Toxins in the bloodstream tend to settle in the endrometrial tissue. When this tissue is shed each month, so are the toxins. Heavy periods may be a toxin-excretion technique.

A deficiency in vitamin A or iron , or hypothyroidism may also cause heavy periods. Painful heavy periods may be linked to endometriosis, fibroids, pelvic inflammatory disease, or the use of an intrauterine device (IUD). A single heavy period that takes place later in the cycle may be a miscarriage.

Tampon use

Many women use tampons to absorb their monthly flow. It has been estimated that the average tampon user will use 11,400 in her lifetime. There has been much controversy over the safety of tampons. The use of high-absorbency tampons has been shown to cause toxic shock syndrome (TSS), a bacterial infection caused when tampons left in too long create tiny breaks in the vaginal lining and allow bacteria to enter the blood stream. Symptoms of TSS are high fever , rash, muscle and joint aches, and diarrhea. TSS is now uncommon, but women have died from it in the past.

To reduce the risk of TSS, the United States Food and Drug Administration (FDA) recommends that women use the lowest absorbency tampon required to meet their needs. It is also suggested that tampons be left in for no longer than four to eight hours. Alternatives to tampons are sanitary pads, reusable menstrual collection cups, and washable cloth pads.

A more recent controversy was sparked in the early 1990s over the use of dioxin in tampons. Dioxin is a chemical byproduct of bleach that is a carcinogen. Tampons in the United States are bleached with chlorine during production so they will have a fresher appearance. Research conducted using monkeys has shown that dioxin exposure may be linked to endometriosis.

In 1992, an investigation revealed that FDA scientists had found trace amounts of dioxin in some tampons. Further FDA research has determined that the tampons currently manufactured are done so through the use of a dioxin-free process. However, trace amounts of dioxin may be absorbed from the air, water, or ground. These levels are generally nondetectable, and according to the FDA, do not pose a health risk.

Premenstrual syndrome

Premenstrual syndrome (PMS) is a condition that occurs during the premenstrual phase of the menstrual cycle. The cause is unclear but theories include: abnormal hormone levels, other biochemical abnormalities, inappropriate diet, nutrient deficiencies, psychological factors, or a combination of many factors.

Emotional and mental symptoms include fatigue, mood swings, irritability, nervousness, confusion, depression , tearfulness, and anxiety . Physical symptoms are bloating, discomfort, breast tenderness, cravings, weight gain, acne , change in bowel movements, joint pains, and dizziness .

Other menstrual problems

• A missed period can be caused by pregnancy, stress , increased exercise, emotions, grief, and illness, among others.
• Metrorrhagia is bleeding in between normal episodes of menstruation. It may be caused by ovulation, hormonal factors, cervical lesions, or uterine cancer.
• Polymenorrhoea is bleeding associated with menstrual cycles that are shorter than 21 days. It may be caused by hormonal or ovulatory problems.
• Oligomenorrhea is infrequent menstruation with 35 days to six months between menstrual cycles. Researchers have discovered that women with a menstrual cycle of 40 days or longer are twice as likely as women with average-length cycles to develop type II (adult-onset) diabetes mellitus . It is thought that long or highly irregular menstrual cycles may be associated with insulin resistance.

Diagnosis

Menstrual problems can be diagnosed and treated by gynecologists. Most menstrual problems would be diagnosed by performing a detailed medical history (with an emphasis on menstrual history) and a physical exam, which would include a pelvic exam. Pelvic exams have two components: the manual exam and the speculum exam. During the manual exam, the doctor inserts one or two fingers into the vagina and presses his or her other hand on the lower abdomen to feel the uterus and ovaries. A speculum exam involves inserting a speculum (a metal or plastic tool for opening the vagina) to allow viewing of the vagina and cervix, and to obtain smears for Pap testing (sampling of cervical cells) or culture if an infection is suspected.

Ultrasound exam, in which internal organs are visualized using sound waves, may be performed. Abnormal findings from the examination and laboratory tests may warrant laparoscopy in which a thin, wand like instrument is inserted into an incision in the belly button to visualize abdominal organs.

Urine tests may be performed to diagnose pregnancy or infection. Blood tests to determine hormone levels, as well as other blood parameters, may be performed. Patient history and physical exam findings may suggest specific illnesses that would require additional laboratory testing.

The patient may be asked to fill out a diary in which daily menstrual symptoms are recorded over a period of three to six months. In some cases, the patient may be referred to a psychiatrist for evaluation for PMDD.

Treatment

There are many alternative treatments for menstrual problems. Because menstrual difficulties may be due to a serious condition, patients should consult a doctor before self-treating.

Diet

Phytoestrogens are estrogen-like compounds produced by certain plants. Food sources of phytoestrogens include soy products, flaxseeds, chick peas, pinto beans, french beans, lima beans, and pomegranates. Phytoestrogens can lighten menstruation and lengthen menstrual cycles. On the other hand, researchers have found that women who were fed soy-based formulas in infancy instead of cow's milk are more likely to report heavy menstrual bleeding and painful periods in adult life.

PMS symptoms may be relieved by avoiding caffeine , sugar, salt, white flour, red meat, dairy, butter, monosodium glutamate (MSG), fried foods, and processed foods during the two weeks prior to menstruation. Food that help to fight PMS include steamed green vegetables, salad, beans, grains, and fruit. To obtain essential fatty acids (omega-3 and omega-6) women can eat flaxseeds, sesame seeds, pumpkin seeds, salmon, mackerel, and tuna.

Herbal remedies and Chinese medicine

A variety of herbal remedies may alleviate symptoms associated with menstrual problems. These include:

• black cohosh (Cimicifuga racemosa ): mood swings, tension, establishing ovulation (an important source of phytoestrogens). The German Commission E, however, states that women should not take black cohosh for menstrual problems for longer than six months because of the risk of side effects.
• black haw (Viburnum prunifolium ): cramps
• chamomile (Matricaria recutita ): mood swings, tension, and cramps
• cramp bark (Viburnum opulus ): cramps
• dandelion (Taraxacum dang gui ): fluid retention and bloating
• dong quai (Benincasa cerifera ): PMS symptoms, cramps, irregular cycles, heavy bleeding, or bleeding in between cycles
• fenugreek (Trigonella foenum-graecum ): irregular bowel movements
• feverfew (Chrysanthemum parthenium ): headaches and PMS symptoms
• ginger (Zingiber officinale ): cramps, irregular cycles, heavy bleeding, or bleeding in between cycles
• goldenseal (Hydrastis canadensis ): heavy bleeding
• horsetail (Equisetum arvense ): heavy bleeding
• licorice: PMS symptoms
• milk thistle (Silybum marianum ) extract: heavy bleeding
• nettle (Urtica dioica ) extract: heavy bleeding
• peppermint (Mentha piperita ): mood swings and tension
• raspberry tea: cramps, irregular cycles, heavy bleeding, or bleeding in between cycles
• red clover (Trifolium pratense ): phytoestrogen source
• rosemary (Rosmarinus officinalis ): cramps
• shepherd's purse (Capsella bursa–pastoris ): heavy bleeding
• St. John's wort (Hypericum perforatum ): depression associated with PMS
• valerian (Valeriana officinales ): mood swings and tension
• vitex: PMS symptoms
• wild yam: phytoestrogen source
• yarrow (Achillea millefolium ): cramps

Supplements

The following supplements may treat menstrual problems:

• Calcium deficiency may be associated with PMS
• Iron supplementation can treat anemia
• Magnesium pidolate supplementation reduced dysmenorrhea symptoms by up to 84%, especially on days two and three
• Niacin may help to relieve cramps
• Omega-3 fatty acids deficiency is associated with dysmenorrhea pain (in one small study, patients taking omega-3 fatty acids had lower pain scores)
• Thiamine (vitamin B₁) cured dysmenorrhea in 87% of the patients for up to two months after treatment
• Vitamin A may be useful to treat heavy bleeding in women who have vitamin A deficiencies
• Vitamin B complex may help hormonal function, prevent anemia, reduce water retention, and relieve stress
• Vitamin E may reduce mood swings and menstrual cramps

Other treatments

Other treatments for menstrual problems include:

• Acupressure . Acupressure can relieve pain, reduce stress, and improve circulation.
• Acupuncture . Treatment is associated with improvement or cure of dysmenorrhea and PMS and decreased use of pain medications. A National Institutes of Health (NIH) panel concluded that acupuncture may be a useful treatment for menstrual cramps.
• Aromatherapy. Massage with the essential oils rose, ylang-ylang, bergamot, and/or geranium oils for mood swings; lavender , sandalwood, and clary sage oils for menstrual cramps; and chamomile, cypress, melissa, lavender, and jasmine oils for irregular menstruation or amenorrhea.
• Biofeedback . Weekly biofeedback therapy for 12 weeks led to significant reduction in PMS symptoms.
• Chiropractic. Spinal manipulation can help to ease cramps.
• Exercise. Regular, moderate aerobic exercise reduces or eliminates menstrual pain, improves PMS, reduces the amount of menstrual bleeding, reduces the risk for endometriosis, and reduces cyclic breast pain and cysts. Yoga stretching can relieve back and thigh pain.
• Homeopathy. Homeopathic remedies include: lachesis or sepia for PMS, cimicifuga, colocynthis, or magnesia phosphorica for cramps, and pulsatilla or aconitum for irregular menstruation or amenorrhea.
• Hydrotherapy. Soaking in a hot tub or using a moist heating pad relaxes uterine muscles which relieves cramping.
• Reflexology . Ear, hand, and foot reflexology led to a significant decrease in PMS symptoms that lasted for several months following treatment.
• Transcutaneous electric nerve stimulation (TENS). In four small studies using TENS for the treatment of dysmenorrhea, 42%–60% of the patients experienced at least moderate relief of symptoms. TENS worked faster than naproxen and there was less need for NSAIDs.

Allopathic treatment

The treatment for amenorrhea depends upon the cause. Primary amenorrhea may require hormonal therapy.

Patients with dysfunctional or abnormal uterine bleeding may be prescribed iron supplements to treat anemia. Naproxen sodium (Aleve) reduces excessive blood loss. Oral contraceptives are often prescribed to treat abnormal bleeding. High doses of estrogens may cause vomiting, which means that antiemetics (drugs to prevent vomiting) may also be necessary. Excessive bleeding may require hospitalization for observation and treatment.

Primary dysmenorrhea is usually successfully treated with nonsteroidal anti-inflammatory drugs (NSAIDs); aspirin is not strong enough to be effective. NSAIDs are numerous and include ibuprofen (Advil, Motrin, Nuprin), Naproxen (Aleve), and fenamates (Meclomen). Oral contraceptives (birth control pills) may be used if NSAIDs fail. Treatment of secondary dysmenorrhea involves treating the causative condition and may involve medications or surgery.

Because the cause(s) of PMS are unclear, treatment usually focuses on relieving symptoms.

With regard to PMDD, medications that have been reported to be effective in treating it include the tricyclic antidepressants and the selective serotonin reuptake inhibitors (SSRIs). Effective treatments other than medications include cognitive behavioral therapy (CBT), aerobic exercise, and dietary supplements containing calcium, magnesium, and vitamin B₆.

Expected results

Most menstrual problems can be successfully treated using conventional or alternative treatments.

Prevention

Avoiding sodium and caffeine may reduce some menstrual symptoms. Regular moderate aerobic exercise or yoga is often beneficial for menstruation difficulties. Getting yearly pelvic exams and Pap smears will help to identify problems before they become advanced.

Resources

BOOKS

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision. Washington, DC: American Psychiatric Association, 2000.

"Menstrual Abnormalities and Abnormal Uterine Bleeding." Section 18, Chapter 235 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.

Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part II, "CAM Therapies for Specific Conditions: Menstrual Symptoms, Menopause, and PMS." New York: Simon & Schuster, 2002.

Trickey, Ruth. Women, Hormones and the Menstrual Cycle: Herbal and Medical Solutions from Adolescence to Menopause. St. Leonards, Australia: Allen & Unwin, 1998.

Wolf, A.S., K. Marx, and U. Ulrich. "Athletic Amenorrhea." In Adolescent Gynecology and Endocrinology: Basic and Clinical Aspects. Edited by George Creatsas, et al. New York: The New York Academy of Sciences: 1997.

Ying, Zhou Zhong, and Jin Hui De. "Menstrual Disorders." In Clinical Manual of Chinese Herbal Medicine and Acupuncture. New York: Churchill Livingston, 1997.

PERIODICALS

Aegerter, Ch., D. Friess, and L. Alberio. "Menorrhagia Caused by Severe Hereditary Factor VII Deficiency. Case 1." Hämostaseologie 23 (August 2003): 99–102.

Chez, Ronald A., and Wayne B. Jonas. "Complementary and Alternative Medicine. Part II: Clinical Studies in Gynecology." Obstetrical and Gynecological Survey 52 (1997): 709–715.

Donaldson, M. L. "The Female Athlete Triad. A Growing Health Concern." Orthopedic Nursing 22 (September-October 2003): 322–324.

"Exposure to Soy-Based Formula in Infancy." British Journal of Ophthalmology 85 (November 2001): 1396.

Halbreich, U., J. Borenstein, T. Pearlstein, and L. S. Kahn. "The Prevalence, Impairment, Impact, and Burden of Premenstrual Dysphoric Disorder (PMS/PMDD)." Psychoneuroendocrinology 28 (August 2003) (Suppl 3): 1–23.

McDonald, Claire, and Susan McDonald. "A Woman's Guide to Self–Care: Everything You Need to Know to Treat the Symptoms of Menstruation, Pregnancy, and Menopause Safely and Naturally." Natural Health (January–February 1998): 121+.

Meduri, G., P. Touraine, I. Beau, etc. "Delayed Puberty and Primary Amenorrhea Associated with a Novel Mutation of the Human Follicle-Stimulating Hormone Receptor: Clinical, Histological, and Molecular Studies." Journal of Clinical Endocrinology and Metabolism 88 (August 2003): 3491–3498.

Rapkin, A. "A Review of Treatment of Premenstrual Syndrome and Premenstrual Dysphoric Disorder." Psychoneuroendocrinology 28 (August 2003) (Suppl 3): 39–53.

Solomon, Caren G., Frank B. Hu, Andrea Dunaif, et al. "Long or Highly Irregular Menstrual Cycles as a Marker for Risk of Type 2 Diabetes Mellitus. Journal of the American Medical Association 286 (November 21, 2001): 2421–2426.

ORGANIZATIONS

American College of Obstetricians and Gynecologists (ACOG). 409 12th Street, SW, P. O. Box 96920, Washington, DC 20090-6920. <http://www.acog.org>.

American Psychiatric Association (APA). 1400 K Street, NW, Washington, DC 20005. (888) 357-7924. <http://www.psych.org>.

Feminist Women's Health Center. 106 East E Street, Yakima, WA 98901. (509) 575-6473 x112. Info@fwhc.org. <http://www.fwhc.org>.

National Women's Health Network. 514 10th Street NW, Suite 400, Wash., DC 20004. (202) 628-7814. <http://www.womenshealthnetwork.org>.

Belinda Rowland

Rebecca J. Frey, PhD

menstruation is the periodic shedding of the endometrium (lining of the uterus) accompanied by blood loss, that identifies the reproductive years of a woman's life. The first menstruation (menarche) usually occurs at puberty (typically between the ages of 11 and 16) and menstrual periods continue until the menopause around the age of 45–50. However, menstruation does not occur during pregnancy and can be suppressed or disrupted in women who are breast-feeding. This was noted by the scientist and philosopher, Aristotle (384–22 bc), who believed that pregnant women did not menstruate because the seed of the male caused blood to coagulate into an egg from which the fetus developed. Milk was also thought to be formed from menstrual blood because of the absence of menstruation in lactating women.

The old ideas as to why women menstruate stemmed from the teachings of Hippocrates (c.400 bc) who believed that health was governed by the balance of the four body fluids or humours — blood, phlegm, black bile, and yellow bile. Thus menstruation was seen as a means of getting rid of excess blood to prevent the body filling with this humour, upsetting the balance and causing illness. This theory was finally disproved by John Davidge in 1814, who pointed out that a woman might only lose a few teaspoons of blood in a typical menstrual flow, while the loss of a much greater amount of blood through blood-letting (cutting the veins) did not prevent menstruation. He concluded that menstruation, rather than being a means of getting rid of excess blood, could be attributed to some odd condition of the ovaries which excited the blood vessels of the womb. In essence his premise was correct.

Menstruation is the culmination of a complex series of hormonal events associated with the cyclical production of a mature egg within the ovary and the release of this egg for fertilization. In the first half of the menstrual cycle, ovarian follicles, containing an egg, develop, and produce increasing amounts of oestrogen. This sex hormone stimulates a build-up of the lining of the womb and the growth of spiral arteries into this thickened lining. After ovulation, which occurs around day 14 of the cycle, the empty follicle in the ovary becomes a corpus luteum. This produces high concentrations of progesterone and some oestrogen. The progesterone further increases the thickness of the uterine lining and causes it to secrete a fluid which will nourish a fertilized egg and encourage implantation of the embryo. If fertilization does not occur the corpus luteum breaks down towards the end of the cycle and so the endometrium loses its hormonal support from the ovary. As a consequence the endometrium literally dies, and the cells of this lining are shed along with some loss of blood from the spiral arteries which have grown into the lining of the womb. Menstrual bleeding usually lasts 3–7 days, although endometrial regeneration can begin as early as the third day after the beginning of menstruation. Interestingly, only in man, apes, and Old World monkeys is the endometrium shed. In most other mammals the endometrium is resorbed at the end of each cycle and there is no bleeding — this is probably related to the absence of spiral arteries.

While the shedding of the uterine lining actually signifies the end of each reproductive cycle, the first day of menstruation is defined for convenience and accuracy as the beginning of a new menstrual cycle. Typically each cycle lasts between 25 and 34 days in 95% of women, with 28 days being the average. Hence the term ‘menstruation’, since it tends to recur at monthly intervals. Total blood loss during each menstruation varies from cycle to cycle, and in different women at different stages of their reproductive life. However, the average blood loss is about 50–60 ml (a teaspoon holds about 5 ml), although it can vary from about 10–80 ml. Excessive loss of blood (menorrhagia) can lead to iron-deficiency anaemia.

Many myths, legends, and taboos have grown up around menstruation throughout the centuries, but all with the underlying sentiment that menstruating women are unclean and capable of producing bad effects on the world about them. It became a focus of religious observance. For example, Hindu women are not supposed to prepare their husbands' food when they are menstruating. Those Moslem women who are normally allowed to pray in a Mosque may not do so during menstruation. Some Buddhists think it is wrong to enter a temple during menstruation and Jews are supposed to refrain from sexual intercourse during this time. In medieval times menstruating women were excluded from going to church and the Church of England has a service for ‘The Churching of Women’, a ceremony to be performed when a woman has had her first menstruation after the birth of a child. And so from the early teaching of Hippocrates, right through the centuries menstruation has been seen as a way of getting rid of something undesirable, unclean and potentially harmful. No wonder such derogatory terms as ‘the curse’ came into existence.

Saffron Whitehead

menstruation periodic flow of blood and cells from the lining of the uterus in humans and most other primates, occurring about every 28 days in women. Menstruation commences at puberty (usually between age 10 and 17). The onset of menstruation, called menarche, signals the body's coming readiness for childbearing. It continues, unless interrupted by pregnancy until menopause (around age 50).

There have been many myths and taboos associated with menstruation. Some cultures isolated women or thought the menstrual flow "unclean" or a "curse." More recent taboos against exercise or sexual intercourse during menstruation are slowly lifting. Some scientists have asked why menstruation occurs at all—why the uterine lining does not remain in place, regenerating itself as other parts of the body (such as the skin and digestive tract) do. One theory is that menstruation is a defense against microbes that enter the uterus with incoming sperm.

The Menstrual Cycle

In the first phase of each cycle, the lining, or endometrium, of the uterus undergoes rapid proliferation of cells and venous channels in preparation for pregnancy. Midway through the cycle an ovum (egg) is released from an ovary . If, while passing through the fallopian tube the ovum is fertilized by a sperm, implantation in the uterus occurs and the thickened lining helps support the pregnancy. When the ovum is not fertilized, this tissue and blood are shed. The proliferation of the uterine wall then begins once more in expectation of the next release of an ovum, and if conception does not take place, it sloughs off again. The process continues monthly until pregnancy occurs or until ovulation ceases at menopause.

The natural rhythm of the menstrual cycle may be broken or temporarily halted by hormonal imbalance, malnutrition, illness, or emotional disturbance (see amenorrhea ). Menstruation is controlled by the hypothalamus and the pituitary gland and hormones, such as estrogen , which prepares the lining of the uterus, and progesterone , which helps maintain a pregnancy.

Dysmenorrhea and Premenstrual Syndrome

Many women experience painful menstruation, or dysmenorrhea. The uterine contractions that result in the cramps experienced by these women appear to be caused by hormones called prostaglandins that are produced in the second half of the cycle. Oral contraceptives and other drugs that reduce the production of prostaglandins are sometimes used in treatment. Other women experience symptoms such as behavioral changes, breast tenderness, and fatigue during the week immediately preceding menstruation, a condition referred to as premenstrual syndrome , or PMS.

Bibliography

See publications of the National Institute of Child Health and Human Development; Boston Women's Health Book Collective, Our Bodies, Ourselves for the New Century (1998).

Menstruation. The periodic loss of blood from the womb: as such, it has evoked in all religions responses of caution, since blood, connected as it is with life and death, is regarded as potentially threatening, and therefore polluting.

Even in a religion, Christianity, which is supposed to have transcended the detail of the law, the tenacity of this fear has persisted, especially in those parts of the Church dominated by male celibates (e.g. the Roman Catholic refusal until very recently, 1992, to allow girl servers into the sanctuary). The dissonance now set up, in law- or custom-based religions, between modern knowledge and religious requirement is an increasing point of stress.

menstruation (menses) (men-stroo-ay-shŏn) n. the discharge of blood and fragments of endometrium from the vagina at intervals of about four weeks in women of child-bearing age (see menarche, menopause). The normal duration of discharge varies from three to seven days. anovular m. discharge that takes place without previous release of an egg cell from the ovary. vicarious m. bleeding from a mucous membrane other than the endometrium when normal menstruation is due. See also amenorrhoea, dysmenorrhoea, menorrhagia, oligomenorrhoea.

men·stru·a·tion / ˌmenstroōˈāshən; menˈstrā-/ • n. the process in a woman of discharging blood and other materials from the lining of the uterus at intervals of about one lunar month from puberty until menopause, except during pregnancy.

menstruation See menstrual cycle.