What are periods?

A period (also called menstruation) occurs as part of a woman's normal menstrual cycle.

During a period, the uterus sheds its lining (also called the endometrium) that developed during the previous menstrual cycle and this passes out through the vagina.


The periodic shedding of the lining of a woman's uterus. Typically occurring about every four weeks between puberty and menopause (except during pregnancy). The menstrual period varies between individuals, but typically lasts 3-5 days.


The hollow organ of the female reproductive system that is responsible for the development of the embryo and fetus during pregnancy. Also known as the womb.

When do women get their period?

Girls generally begin having their periods between 8-16 years of age, as part of the changes that occur during puberty, with the average age of a girl having her first period being 12 years. Most women continue to have periods (except during pregnancy) until menopause occurs, usually sometime between their late 40s and early 50s.

An average menstrual cycle is 28 days, although it can vary from 21-35 days.


The period of life, initiated by hormonal signals, in which a person becomes capable of reproduction as the sexual and reproductive organs mature.

The menstrual cycle

The menstrual cycle is a monthly cycle of changes that the female body goes through to prepare for a potential pregnancy. Control of the menstrual cycle is complex, involving a number of organs (the uterus and ovaries), glands (the hypothalamus and pituitary gland in the brain) and various hormones. These hormones rise and fall throughout three phases of the menstrual cycle - the follicular phase, ovulation and the luteal phase.

Follicular phase

The follicular phase of the menstrual cycle begins on the first day of the period. The hypothalamus causes the pituitary gland to release follicle-stimulating hormone (FSH). This causes the ovaries to produce follicles, which are immature eggs, and estrogen. The estrogen stimulates the uterus to begin thickening its lining in preparation for ovulation.


Around halfway through the cycle, about two weeks before the start of the next period, there are rising levels of luteinizing hormone that causes the release of a mature egg (ovum) from one or two of the follicles in the ovaries. The egg travels down the fallopian tubes towards the uterus. For around 24 hours, it is able to be fertilized by sperm. If this happens, the fertilized egg then embeds itself in the lining of the uterus and a pregnancy begins.

Luteal phase

After the egg is released, the follicle in the ovary develops what is called a corpus luteum. The corpus luteum then produces the hormones progesterone and estrogen, which help to maintain the thickened lining of the uterus.

If the egg is not fertilized, around the 22nd day of the cycle, the corpus luteum begins to shut down and stops producing progesterone. This triggers the uterus to begin shedding its lining and begin the next menstrual cycle.

If the egg is fertilized, it produces hormones that help maintain the uterus and corpus luteum and so stop the menstrual cycle for the length of the pregnancy.

A diagram showing the four stages of the menstrual cycle.The menstrual cycle. 

Fallopian tubes

The tube-like structures connecting a woman's uterus to her ovaries. Eggs released by the ovaries travel to the uterus via the fallopian tubes.


A chemical substance secreted in one part of an organism and transported to another part of that organism, where it has a specific effect.


A small part of the brain that carries out many functions, in particular the communication between the nervous system and the endocrine system (via the pituitary gland).


One of a group of steroid hormones involved in the development and maintenance of female sex characteristics. These are the primary female sex hormones.


Female organs located on either side of the uterus. Each ovary produces eggs that travel along the fallopian tubes to the uterus.


The phase of the female menstrual cycle during which an ovum (egg) is released from one of the woman's two ovaries.


A mature female reproductive cell that is released from the ovary during ovulation, also called an egg.


The mature male sex cell that fertilizes the female ovum.


The hollow organ of the female reproductive system that is responsible for the development of the embryo and fetus during pregnancy. Also known as the womb.

Luteinizing hormone

A type of hormone produced by the pituitary gland. In females, this hormone triggers the cyclical release of an egg, roughly each month. In males, it stimulates testosterone production.

Variations in your cycle

For young women, it can take a number of years for their menstrual cycle to settle down into a regular pattern. Once your cycle is regular, it may vary sometimes by a few days for a range of reasons including illness, stress, changes in your lifestyle, your weight and what you eat. However, if your cycle changes significantly for more than a couple of months, becomes irregular or stops completely for six months, it may be a sign of an underlying health condition that needs investigating by your doctor.

To understand what is normal for you, it can be helpful to record when your period starts, how long it lasts, as well as when any concerning symptoms occur.


The word ‘stress’ can have a variety of meanings, but generally describes the physical and mental responses of the body to a demand placed upon it. Often used to describe conditions where the demand is high or unable to be resolved and creates anxiety and tension.

Before your period

Premenstrual syndrome (PMS) describes a range of physical and psychological symptoms that can occur in the two weeks before a woman has her period. Most women do experience some level of symptoms due to PMS, however, they generally improve within a day or so of a period starting.

During your period

Periods and menstrual flow vary considerably between different women, so there is no single description of a 'normal' period.

Women can manage their periods with a range of products including the following:

  • Sanitary pads - these are designed to line your underwear and absorb menstrual flow. They are generally changed every few hours, and;
  • Tampons, which are thin cylinders of absorbent material that are inserted into the vagina. They are recommended to be changed at least once every 6-8 hours, more frequently when menstrual flow is heavy.

A rare medical condition called toxic shock syndrome (TSS) can be associated with tampon use, particularly if tampons are left in for an extended period of time. While the causes of TSS are not completely understood, it is thought to be due to toxins produced by bacteria such as Staphylococcus aureus and Streptococcus pyogenes. Symptoms of TSS include fever, headaches, vomiting and diarrhea and requires emergency medical treatment.

Menstrual flow

During a period, bleeding from the vagina usually lasts around 2-7 days and is usually heaviest in the first two days.

Menstrual flow:

  • Consists of blood, cells and mucus from the lining of the uterus (endometrium). Small pieces of the endometrium may be visible;
  • May include some clots of blood;
  • Can change in color over a period. Often it is bright red initially and may become brown or black towards the end of a period. This is because flow later in the period is slower and has been exposed to more oxygen, and;
  • May slow down or temporarily stop during the third or fourth day and then resume again.

The amount of menstrual flow varies considerably between women and can vary between cycles. Estimates suggest up to 80 milliliters is common, but for some women a heavier flow will be quite normal.

If the menstrual flow is so heavy that you need to change a pad or tampon more than once an hour, this is not considered normal and requires investigation with your doctor. Passing large clots of blood can also be a sign of problems.

Also, even if it is normal for you, if your flow is so heavy that it is causing you problems and distress, your doctor can advise on treatments that are available to help reduce it.

Period pain

Period pain is common and many women will experience it at some time during their lives. It often affects younger women soon after their periods start and tends to lessen as women get older.

Period pain is caused by prostaglandin hormones, which cause the muscle layer of the uterus to cramp or contract. As well as pain in the lower abdomen, women can also experience back pain.

Period pain:

  • Generally occurs on the first day of your period, although for some women it can last longer or start in the days before their period begins, and;
  • Is usually relatively mild, so that it can be managed by applying warmth (such as a hot pack), or with mild pain medications such as acetaminophen, naproxen or ibuprofen.

Pain that is so severe that you need to take time off work, or take pain medications regularly, or that wakes you up at night is not considered normal and may need investigation with your doctor.

Woman with stomach pain.Period pain can cause abdominal pain. 

Menstrual headaches

Women can be more likely to experience headaches or migraines around the time of their periods. If you suffer headaches or migraines that aren't able to be well managed by mild pain medications, other treatments are available. Your doctor can advise what options may be most suitable for you.


The part of the body that lies between the chest and the pelvis.


The fundamental unit of life; the simplest living unit that can exist, grow, and reproduce independently. The human body is composed of trillions of cells of many kinds.


A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.


The hollow organ of the female reproductive system that is responsible for the development of the embryo and fetus during pregnancy. Also known as the womb.

Bleeding between periods

It can take a number of years for some young women to establish a regular cycle and bleeding pattern. Some young women will spot slightly (pass a small amount of blood) during ovulation, about 14 days before their period.

Additionally, it can be normal for some women to:

  • Spot slightly in the days just before their period, or;
  • Bleed between periods when taking contraceptives or hormonal treatments.

Otherwise, bleeding between periods or after sex can be an indication of infection or other medical conditions, particularly if such bleeding is not usual for you. In rare cases, cancer can cause bleeding between periods, so it is important that it is investigated by your doctor.

After menopause, any bleeding may also be a sign of an underlying medical condition and needs to be checked by a doctor.


The phase of the female menstrual cycle during which an ovum (egg) is released from one of the woman's two ovaries.


Relating to hormones, which are chemicals secreted in one part of an organism and transported to another part of that organism, where they have a specific effect.

Seeing your doctor

If you have any concerns regarding your period and whether it is normal or not, you can always see your doctor or gynecologist.

They will ask you about your symptoms and may recommend tests, which may include:

A doctor providing a physical examination for a female patient.A doctor or gynecologist will perform routine examinations if you have period concerns. 

Dilatation and curettage

A surgical procedure in which the cervix is opened up by instruments called dilators to allow access to the uterus. The uppermost layer of the lining of the uterus is gently scraped off.


A healthcare professional who specializes in the female reproductive system.


A chemical substance secreted in one part of an organism and transported to another part of that organism, where it has a specific effect.


A hysteroscopy is performed to help diagnose or treat a uterine problem. The uterus is examined with a straw-like tube with a camera called a hysteroscope.


An essential mineral required by the body. Iron is part of a protein in the blood called hemoglobin, which carries oxygen around the body.

Pelvic examination

An examination performed by your doctor or nurse that involves a speculum examination with a duck-bill instrument and an internal examination in which they may put two gloved fingers inside your vagina to check for lumps or tender regions.

Pelvic ultrasound

A scan that uses a device that emits high-frequency sound waves to produce images of the internal structures of your pelvis. It may be performed over your abdomen or through your vagina.


  1. About Periods | The Royal Womens Hospital. Accessed August 28 2014. link here Random House. The Womens Health Book. Random House Australia 2014.
  2. Heavy Periods (menorrhagia) - NHS Choices. Accessed August 28 2014. link here
  3. Menstrual Cycle | Better Health Channel. Accessed August 28 2014. link here
  4. Periods - Symptoms - NHS Choices. Accessed August 28 2014. link here
  5. Problem Periods | The Royal Womens Hospital. Accessed August 28 2014. link here
  6. Toxic Shock Syndrome | Better Health Channel. Accessed August 28 2014. link here

FAQ Frequently asked questions