Updated 19 May 2015


Menstruation is the periodic discharge of blood and tissue from the lining of the uterus.



  • Menstruation is the periodic discharge of blood and tissue from the lining of the uterus, occurring about every 28 days in women of reproductive age.
  • The first menstrual cycle occurs at puberty and repeats throughout life until menopause, unless interrupted by pregnancy or long-acting hormonal contraception.
  • Most girls have their first menstrual period, called menarche, between the ages of nine and 16.
  • Some of the common menstrual problems, such as cramps, can often be relieved effectively with home remedies.
  • Menstruation has a typical pattern of duration, frequency and associated symptoms for each woman. When there is noticeable deviation from this pattern, a menstrual disorder may be present requiring medical attention.

Alternative names

menses, menstrual periods


Menstruation is the normal, periodic discharge of blood and tissue from the lining of the uterus (womb), occurring about every 28 days in women of reproductive age. The onset of menstruation, called menarche, happens at puberty. The menstrual cycle will repeat throughout life, unless interrupted by pregnancy or long-acting hormonal contraception, until menopause (cessation of menstruation, around 52).

There have been many myths and taboos associated with menstruation. Some cultures continue, as many have in the past, to isolate or constrain menstruating women, and consider menstrual flow to be shameful or "unclean". However, in general, attitudes are now becoming much more positive and open towards this natural process.

The reason why women menstruate is linked to reproduction and the rather short lifetime of an unfertilised egg once it has been released from the ovary at ovulation. If the egg would become fertilised, the endometrium, which undergoes changes in preparation for the implantation of the developing embryo, would not be shed but would form an integral part in the growth of the pregnancy. If the egg is not fertilised, the egg dissolves, followed by the shedding of the endometrium. A new endometrium will be built up with the next egg in the next cycle.


The onset of menstruation is called menarche.

A girl is born with her full complement of eggs stored in her ovaries. Usually, one egg is released each month from the time of ovulation which occurs 14 days before the next menstrual period. At puberty (which starts between the ages of about eight and 14), several events follow in a pre-programmed sequence under the influence of brain hormones, hormones from the pituitary gland, the adrenal glands and the ovaries. This leads to a spurt in growth, the beginning of breast development followed by the development of pubic and axillary hair.

The ovaries start functioning by producing eggs and hormones called oestrogens and progesterone which influence the body to take up the typical female shape and prepare various organs for a possible pregnancy.

Menarche is a relatively late occurrence in this sequence of events and the first period is usually very light - only a few spots of blood or a brown sticky stain.

Menstrual periods are often irregular for the first few years after menarche. The intervals may be shorter (about three weeks) or longer (about six weeks) than average, or there may be only three or four periods a year. The menstrual cycle will become more regular with time, although several women continue to have irregular periods as adults.

The reason for this is that young girls after menarche do not necessarily ovulate right from the beginning, and it may take up to two years before their menstrual cycles with regular ovulations, followed by menstruations, become established. A similar event in reversed order occurs in women close to their menopause, when ovulations become irregular, although menstruations may still be at regular intervals for some months.

Most girls get their first menstrual period between the ages of nine and 16, usually about one-and-a-half to two years after their breasts begin to develop, and after the appearance of pubic hair and the growth spurt. Genetics seem to be a determining factor: many girls have their first period at roughly the same age as the time of menarche of their mothers. About six months before her first period, a girl might notice an increased amount of clear vaginal discharge.

The menstrual cycle

The two ovaries, each containing thousands of ova (eggs), are positioned on either side of the uterus in the pelvis. The fallopian tubes form the connecting passage from the ovaries to the uterus.

Every month, either the left or the right ovary produces a follicle, a little fluid-filled blister. This is done under the influence of a follicle stimulating hormone (FSH) from the pituitary gland in the brain. The follicle contains an egg and surrounding fluid consisting of oestrogens. The egg will be released during ovulation which occurs 14 days before the next menstrual period. After ovulation, the empty follicle is filled up again, initially with blood, which later changes into progesterone, the dominating hormone of the second half of the menstrual cycle.

Oestrogen and progesterone cause certain changes in the endometrium, the lining of the uterus. In the first phase (proliferative phase) of each menstrual cycle, the endometrium undergoes rapid proliferation of cells and blood vessels. The lining of the uterus becomes thick in preparation for a potential pregnancy. Midway through the cycle, ovulation occurs which is triggered by the pituitary hormone LH (luteinising hormone): the walls of a follicle in one of the ovaries open and a single mature ovum (egg) is released and taken up by the fallopian tube of the corresponding side. If the ovum is fertilised by a sperm, the fertilised egg is passively moved down the fallopian tube toward the uterus, a journey which takes about four to five days. It will then implant in the uterine lining which has been further prepared by progesterone during the secretory phase, the second phase of the menstrual cycle. After implantation the developing embryo will turn into a fetus which will be born as a baby.

If the ovum is not fertilised, it will start to disintegrate about 24 hours after ovulation. Oestrogen and progesterone levels decline and the reduction of these hormones causes the endometrium to become thin and its blood flow to decrease. 14 days after ovulation, the unused uterine lining breaks down and is shed during menstruation, along with some blood through the cervix and the vagina.

The endometrium then begins to thicken once again. This cycle (an egg being released once a month and the uterine lining thickening and then being shed) will continue to occur almost every month until interrupted by pregnancy or until ovulation ceases at menopause. Menstruation may or may not cease during lactation (breastfeeding).

A menstrual cycle lasts from the first day of one period to the first day of the next. The typical cycle of an adult female is 28 days, although cycles can range between 22 and 35 days. Only 15 percent of women have a 28-day cycle.

The length of the menstrual cycle is determined by the number of days it takes for an ovary to allow a follicle and egg to become mature and to release the egg. The second half of the cycle, ovulation to menstruation, is fairly consistently the same length: menstruation occurs about 14 days after ovulation for nearly all women. The first part of the cycle varies from person to person and from cycle to cycle.

The duration of each menstrual period can also vary: most last for about five days, but some women menstruate for only two or three days, and others for up to eight days.

The menstrual blood loss varies among different individuals too, from about one-and-a-half tablespoons to one-third of a cup (20 to 80 ml) of menstrual fluid. About seventy percent of menstrual fluid is produced by the second day of a period, and 90 percent by the third day. Menstrual flow and duration may also change from month to month in the same individual, and may vary over the course of a lifetime.

The rhythm of the menstrual cycle may be interrupted by hormonal imbalance, malnutrition, illness or emotional stress.

Common menstrual problems

There are several problems which can occur with menstruation. They can vary in severity and some of them can effectively be relieved with home remedies.

Dysmenorrhoea (cramps, menstrual pain)

Over half of women who menstruate have cramps during the first few days of their period. The pain can be a dull ache or sharp and intense or colicky. Menstrual pain is classified as primary or secondary dysmenorrhoea. Primary dysmenorrhoea (cramping) is probably caused by prostaglandins, hormones produced before the beginning and during the first two days of menstruation which affect tension of the uterine muscle.

Menstrual cramps usually start 6-24 months after menarche and tend to become less uncomfortable and sometimes disappear completely as a girl gets older.

Methods to relieve cramping:

  • An over-the-counter pain medication, (e.g. containing a nonsteroidal anti-inflammatory drug, NSAID) can provide relief within 30 – 60 minutes. However, NSAIDs should not be taken for prolonged times since there are certain contraindications, and a doctor should be consulted.
  • A hot water bottle or heating pad can be placed over the lower abdomen.
  • Exercise improves oxygen supply and blood circulation throughout the body, including the pelvis.
  • Relaxation techniques such as massage or deep breathing can help.
  • A diet with increased intake of magnesium, calcium and omega 3 fatty acid containing food such as fish and fish-oil is helpful.

Premenstrual syndrome (PMS)

Premenstrual syndrome (PMS) is a common condition that refers to a group of symptoms experienced as a result of changing hormone levels before and sometimes during menstruation. Symptoms, which may be psychological, behavioural and physical, usually become apparent in the week preceding menstruation. The difference between dysmenorrhoea and PMS can often be made according to the history. In general, the pain with PMS is related to breast tenderness and the feeling of having a bloated abdomen, while in dysmenorrhoea, the pain is a cramping sensation in the lower abdomen. As a rule, PMS abates soon after the start of the period.

The exact mechanism how the monthly change in hormone levels causes PMS, is unknown. There are no hormonal differences in women with or without PMS, and it is assumed that women with PMS may have a different response of their central nervous system to the cyclical variation of their hormones.

There is a large variety of psychological and emotional symptoms which have been described with PMS. Some women experiencing anger, tension, fatigue and depression will have temporary relief by eating food rich in carbohydrates. Caffeine-containing beverages such as coffee, tea and cola should be avoided, since their stimulating effect may worsen tension, irritability and also insomnia (sleeplessness).

Furthermore, food having a high content in salt should also be avoided since it promotes water retention. The retention of fluid may be responsible for some women feeling bloated premenstrually, which is often described subjectively despite the fact that there is no measurable increase in weight or abdominal circumference. One of the explanations for this is a possible redistribution of body fluid into the abdomen or into the intestinal walls.

Other menstrual disorders

Amenorrhoea:absence of periods, classified as primary or secondary. Primary amenorrhoea is no menstruation by age 14 (if combined with lack of development of secondary sexual characteristics), or no menstruation by age 16.5, or no menstruation two years after development of breasts and/or pubic/axillary hair. Primary amenorrhoea may also occur in young athletes or girls with eating disorders who experience delayed puberty.

Secondary amenorrhoea is the absence of periods for at least three months in a woman who has previously had regular monthly periods, and for at least six to 12 months in a woman who normally experiences irregular periods. Absence of periods for a shorter period of time than this is called "delayed menses".

Oligomenorrhoea:scanty menstrual flow, when the interval between periods exceeds 35 days, but not long enough to qualify as amenorrhoea. Most women with oligomenorrhoea also have cycles where no eggs are released. Oligomenorrhoea can progress to amenorrhoea.

Oligomenorrhoea may develop as a result of excessive weight gain or loss, stress, excessive exercise, medical problems such as thyroid or liver dysfunction, or certain medications. Women engaging in seasonal sports may have irregular periods for the months they are involved in sport. In these cases, oligomenorrhoea results from suppressed oestrogen production.

Menorrhagiais defined by unusually heavy and/or prolonged menstruations while the menstrual cycle is still regular. This may be caused by an underlying organic disorder or hormonal problems.

How to handle menstrual flow

The most commonly used products to handle menstrual flow are sanitary pads (or towels) and tampons. Both of them have advantages and disadvantages.

Sanitary pads have the advantage that menstrual blood is collected outside the vagina. There is less risk of disturbing the eco-system of the normal vaginal bacterial flora which, if changed, may lead to infection. Excessive bleeding and an unnatural odour are noticed earlier which is important for women who previously suffered from heavy periods or vaginal infections. Sanitary pads are also advisable for young girls who, in the years soon after menarche when the hymenal ring in virgins is still intact and the vagina is still growing, would feel uncomfortable inserting and removing tampons.

Tampons have the advantage of allowing women to “hide” their menstruation under various circumstances, such as swimming or other types of sport, or wearing tight-fitting clothes. The disadvantage of tampon use is the potential change in the vaginal microflora. If abnormal bacteria are harboured in the vagina (either sexually transmitted or due to selfcontamination with rectal germs), menstrual blood which is accumulated inside the vagina above and within a tampon, can act as a culture medium, allowing micro-organisms to multiply, thus promoting infection.

This also explains why tampon use is associated with a slightly increased risk for toxic shock syndrome (TSS), caused by a bacterial infection. Although serious, toxic shock occurs very infrequently. The risk of TSS can be reduced by maintaining good hygiene, changing tampons regularly (every four hours or more often if the menstrual flow is heavy) and by alternating wearing tampons with pads.

Although good hygiene is important during menstruation, there is no need to use douches or "intimate" deodorant sprays, and most medical experts advise against such products as they can irritate the genital area and increase the risk for infection.

When to call the doctor

A doctor should be consulted if any of the following menstrual problems are experienced:

  • No menstruation by age 16, or three years after the development of secondary sexual characteristics
  • No menstruation by age 14 and absent development of secondary sexual characteristics
  • Absent menstruation for three months in a woman who previously has menstruated regularly and has a negative pregnancy test. (Pregnant women should consult their doctor already after two months amenorrhoea.)
  • Menstrual pain and cramps (dysmenorrhoea) not alleviated by home remedies, or other menstrual problems interfering with normal daily life.


Updated by Dr Judith Kluge,MB ChB, FCOG (SA), MRCOG. Dept of Obstetrics & Gynaecology, Tygerberg Academic Hospital, University of Stellenbosch, February 2011


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