Menstrual Cycle

Menstrual Cycles

What happens in the 28 Day monthly period


The Menstrual Cycle

Menstruation is a woman's monthly bleeding. It is also called menses, menstrual period, or period. When a woman has her period, she is menstruating. The menstrual blood is partly blood and partly tissue from the inside of the uterus (womb). It flows from the uterus through the small opening in the cervix, and passes out of the body through the vagina.

Menstruation is part of the menstrual cycle, which helps a woman's body prepare for the possibility of pregnancy each month. A cycle begins on the first day of bleeding and continues up to, but not including, the first day of the next period. The average menstrual cycle is around 28 days long. However, a cycle can range anywhere from 21 days to 35 days or more. The length of a woman's cycle may change a little from month to month. Most menstrual periods can last from 1 to 8 days, with the average being 4 to 5 days.

Periods are a normal part of a woman's life from puberty, around the age of 10-14 (menarche) until its cessation (menopause) about 50. This regular (or not so regular) bleeding is the most noticeable sign of a woman’s menstrual cycle, but it is not the only sign. Getting to know the other, less obvious signs of your cycle can help you become more familiar with your own changing levels of fertility.


What is the menstrual cycle?

The menstrual cycle is regulated by hormones: (LH) luteinizing hormone and (FSH) follicle-stimulating hormone, which are produced by the pituitary gland, also estrogen and progesterone hormones, which are produced by the ovaries. The cycle has three phases: follicular, ovulatory, and luteal.

The menstrual cycle begins with menstrual bleeding (menstruation), which marks the first day of the follicular phase. Bleeding occurs when levels of estrogen and progesterone decrease, causing the thickened lining of the uterus (endometrium) to degenerate and be shed.

menstruation hormonesFollicular Phase
During the first half of this phase, the (FSH) follicle-stimulating hormone level increases slightly, stimulating the development of several follicles. Each follicle contains an egg. Later, as the follicle-stimulating hormone level decreases, only one follicle continues to develop. This follicle produces estrogen.

Ovulatory Phase
The ovulatory phase begins with a surge in (LH) luteinizing hormone and (FSH) follicle-stimulating hormone levels. Luteinizing hormone stimulates egg release (ovulation), which usually occurs 16 to 32 hours after the surge begins. The estrogen level peaks during the surge, and the progesterone level starts to increase.

Luteal Phase
During the luteal phase, levels of the LH and FSH decrease. The ruptured follicle closes after releasing the egg and forms a corpus luteum, which produces progesterone. Later in this phase, the estrogen level increases. Progesterone and estrogen cause the lining of the uterus to thicken more. If the egg is not fertilized, the corpus luteum degenerates and no longer produces progesterone, the estrogen level decreases, the lining degenerates and is shed, and a new menstrual cycle begins.

The length of a woman's menstrual cycle is calculated by the number of days between one period and the next.

A cycle begins on the first day of bleeding and continues up to, but not including, the first day of the next period. Women's cycles range from 21 to 40 days or more, with an average of around 28 days.


What happens during the menstrual cycle?

female internal organsThe follicular phase varies in length, averaging about 13 days of the cycle. This phase tends to become shorter towards the end of the reproductive years (menopause). During this phase, the follicles in the ovaries develop.

The ovulatory phase starts with a surge in the levels of luteinizing hormone and, to a lesser degree, follicle-stimulating hormone. Luteinizing hormone stimulates the dominant follicle to bulge from the surface of the ovary and finally rupture, releasing the egg, usually about 24 hours after the surge in luteinizing hormone begins. This is called ovulation.

About 12 to 24 hours after the egg is released, this surge can be detected by measuring the luteinizing hormone level in the urine.

Around the time of ovulation, some women feel a dull pain on one side of the lower abdomen. This pain is known as mittelschmerz (literally, middle pain). The pain may last for a few minutes to a few hours. The pain is felt on the same side as the ovary that released the egg, but the precise cause of the pain is unknown. The pain may precede or follow the rupture of the follicle and may not occur in all cycles.

Spotting that occurs in the middle of your cycle is normal. This spotting may occur during ovulation. Seeing a spot of blood during ovulation is considered an excellent fertility sign. It is thought that mid-cycle spotting occurs for one of two reasons. First reason is possibly that when the egg bursts through the follicle, a little bleeding may occur. This blood will then make its way out and show up as 'spotting'. Or, during ovulation, the level of estrogens rise, and this sometimes prompts the uterus to shed a bit of lining, which shows up in the form of 'spotting'.

Egg release does not alternate between the two ovaries and appears to be random. If one ovary is removed, the remaining ovary releases an egg every month.

In the second half of the menstrual cycle, the egg begins to travel through the fallopian tube to the uterus. The egg can be fertilized for only a short period (up to about 12 hours) after its release. Fertilization is more likely when sperm are present in the reproductive tract before the egg is released. Progesterone levels rise and help prepare the uterine lining for pregnancy.

The luteal phase follows ovulation. It lasts about 14 days, unless fertilization occurs, and ends just before a menstrual period. In the luteal phase, the ruptured follicle closes after releasing the egg and forms a structure called a corpus luteum, which produces increasing quantities of progesterone. The function of the corpus luteum is to prepare the uterus in case fertilization occurs. The progesterone produced by the corpus luteum causes the endometrium to thicken, filling with fluids and nutrients in preparation for a potential fetus.

Progesterone causes the mucus in the cervix to thicken, making the entry of sperm or bacteria into the uterus less likely. Progesterone also causes body temperature to increase slightly during the luteal phase and remain elevated until a menstrual period begins. This increase in temperature can be used to estimate whether ovulation has occurred (see: Basal Body Temperature).

Spotting that occurs about a week before the cycle is due – and only lasts for less than one day – is possibly considered implantation spotting. This happens as a result of the fertilized egg burrowing into the uterine lining. Or, another reason for seeing implantation spotting may be due to a slight rise in estrogen and drop in progesterone before the corpus luteum takes over the production of progesterone. The corpus luteum takes over the production when the implanted fertilized egg signals the body that pregnancy has occurred and that the lining must be maintained. Keep in mind that spotting that continues for days is not implantation spotting.

In the second part of the luteal phase, the estrogen level increases, also stimulating the endometrium to thicken. In response to the increase in estrogen and progesterone levels, the milk ducts in the breasts increase. As a result, the breasts may swell and become tender.

If the egg is not fertilized, the corpus luteum degenerates after 14 days, and a new menstrual cycle begins. If the egg is fertilized, the cells around the developing embryo begin to produce a hormone called human chorionic gonadotropin (hCG). This hormone maintains the corpus luteum, which continues to produce progesterone, until the growing fetus can produce its own hormones. Pregnancy tests are based on detecting an increase in the human chorionic gonadotropin level.



Early Menopause

The menopause usually starts in the woman's late forties but some women may stop having periods in their thirties or even their twenties. Women affected may at first think that they are pregnant. However, as well as the periods stopping, other symptoms can include hot flushes, night sweats,insomnia, vaginal drying, painful intercourse, loss of libido, genito-urinary infections, thinning of the skin, splitting of the nails, aches and pains, and incontinence. Women may also experience mood changes, anxiety, irritability, poor memory and poor concentration as well as subsequent loss of confidence.

If a doctor suspects premature menopause, the woman may be referred for a laparoscopy. In this procedure, the ovaries are examined by laparoscope (a fibre-optic tube), this allows the doctor to see if the woman's ovaries contain follicles with eggs. Women who experience premature menopause may still achieve a pregnancy, but only through assisted conception.


When am I most fertile?

The few days leading up to ovulation are considered the most fertile in a woman's cycle. This is because sperm can survive for up to seven days in a woman's body (on average they live for 3 days).
If a woman has sex or insemination during the six or seven days before she ovulates, it is likely that the sperm will still be around by the time her egg is released.

One or two days after ovulation are also considered fertile days because a woman's egg can live for about 24 hours after ovulation. If two eggs have matured, the second will be released within 24 hours of the first. From a few days after ovulation until her next bleed, a woman is generally not fertile.

How long does a woman have periods?

Women usually continue having periods until menopause. Menopause occurs on average around the age of 50. Menopause means that a woman is no longer ovulating (producing eggs) and therefore can no longer become pregnant. Like menstruation, menopause can vary from woman to woman and may take several years to occur. Some women have early menopause because of surgery or other treatment, illness, or other reasons.

Missed period

Amenorrhea - the lack of a menstrual period. This term is used to describe the absence of a period in young women who haven't started menstruating by age 16, or the absence of a period in women who used to have a regular period. Causes of amenorrhea include pregnancy, breastfeeding, and extreme weight loss caused by serious illness, eating disorders, excessive exercising, or stress. Hormonal problems (involving the pituitary, thyroid, ovary, or adrenal glands) or problems with the reproductive organs may be involved.

Painful periods or severe menstrual cramps

Dysmenorrhea - painful periods, including severe menstrual cramps. In younger women, there is often no known disease or condition associated with the pain. A hormone called prostaglandin is responsible for the symptoms. Some pain medicines available over the counter, such as ibuprofen, can help with these symptoms. Sometimes a disease or condition, such as uterine fibroids or endometriosis, causes the pain. Treatment depends on what is causing the problem and how severe it is.

Heavy bleeding or unusually long periods

Abnormal uterine bleeding - vaginal bleeding that is different from normal menstrual periods. It includes very heavy bleeding or unusually long periods (also called menorrhagia), periods too close together, and bleeding between periods. In adolescents and women approaching menopause, hormone imbalance problems often cause menorrhagia along with irregular cycles. Sometimes this is called dysfunctional uterine bleeding (DUB). Other causes of abnormal bleeding include uterine fibroids and polyps. Treatment for abnormal bleeding depends on the cause.


Etymology Time

Etymology is the study of the history of words and
how their form and meaning have changed over time

The word "menstruation" is etymologically related to moon. The terms "menstruation" and "menses" come from the Latin mensis (month), which in turn relates to the Greek mene (moon) and to the roots of the English words month and moon — reflecting the fact that the moon also takes close to 28 days to revolve around the Earth (actually 27.32 days). The synodical lunar month, the period between two new moons (or full moons), is 29.53 days long and indicates the rough temporal correlation that some women's menses have with lunar cycles.

English word "menopause" is derived from the Greek word meno-, (month; month, Latin menstruus, pertaining to a month) and -pause derived from the Greek word pause and in turn from the Latin, pausa (to stop, restrain, quit, desist, come to an end)

Menses \Men"ses\, plural noun.
[Latin expression mensis month, plural menses months, and the monthly courses of women.]

Gaelic words for "menstruation" and "calendar" are essentially the same: miosach and miosachan.



  Main Pages


  Pregnancy Tools

Due Date and
Weeks Calculator:
  Last Menstrual Period:

  Estimated Conception:
  Estimated Due Date:
  Since LMP:

  Baby Extras

  Baby Grows





Names Search

Enter a name
or word that
appear in its meaning:


External Links