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What are periods?

A period is the part of the menstrual cycle when a woman bleeds from her vagina for a few days. In most women this happens every 28 days or so.

It's common for women to have a cycle that's longer or shorter than this, from 24 to 35 days.

When do periods start?

Girls have their first period when they start puberty. This can be between the ages of eight and 16 years, although girls most commonly start their periods at about 12 years old. Your periods will continue until the menopause, which usually occurs at the age of around 45 to 55.

The menstrual cycle

Each menstrual cycle starts on the first day of your period (day one) and lasts until the day before your next period begins.

To understand periods and the [menstrual cycle], it helps to know about the reproductive organs inside a woman's body. These are:

  • two ovaries, where eggs are stored, developed and released
  • the womb (uterus), where a fertilised egg implants and a pregnancy grows
  • two thin tubes called fallopian tubes, which connect the ovaries to the womb
  • the cervix, which is the lower part of the womb that connects to the vagina
  • the vagina, which is a tube of muscle connecting the cervix to the outside of the body

In each menstrual cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it (this process is called ovulation). The womb lining gets thicker, ready for a possible pregnancy.

The egg travels down the fallopian tube and you can get pregnant now if the egg meets any sperm.

The egg lives for about 24 hours. If pregnancy doesn't happen, the egg is absorbed into your body. The womb lining comes away and leaves the body, mixed with blood, as a period (the menstrual flow).

Getting pregnant

Your fertile time (when you can get pregnant) can be difficult to pinpoint. It's around the time you ovulate, which in most women is around 12-14 days before the start of their next period.

A woman can't get pregnant if she doesn't ovulate. Some hormonal methods of contraception, such as the combined pill, the patch and the injection work by stopping ovulation.

Body changes

Your body produces different amounts of hormones at different times during your cycle. This can cause changes in your body and your emotions.

Your vaginal secretions, for example, change throughout your menstrual cycle. Around the time of ovulation they become thinner and stretchy, a bit like raw egg white.

You may also have mood swings in the days before your period, or notice your breasts getting swollen and painful.

Premenstrual syndrome (PMS) is a range of symptoms that can affect women in the days before their period.

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Period symptoms

During your period you'll bleed from your vagina for a few days, with the bleeding being heaviest in the first two days.

How long you bleed for depends on your menstrual cycle. Your period could last for three to eight days, but usually lasts for around five days.

The amount of blood you lose depends how heavy your periods are. It's normally around enough to fill between five and 12 teaspoons. Some women bleed more heavily, but there is help if heavy periods are a problem for you. Find out about treating heavy periods.

You can use sanitary towels or tampons to absorb the blood, or a menstrual cup (made of soft silicone) to catch the blood inside your vagina. Towels and tampons are disposable (you throw them away). You can wash menstrual cups and use them again.

If you use tampons, you need to change them regularly. Follow the instructions that come with the packet. This reduces the risk of toxic shock syndrome, which is a rare, serious infection that can affect anyone but is more common in women who are using tampons.

Before your period

The changing levels of hormones in your body before your periods can cause physical and emotional changes. You might notice that your breasts get bigger, you feel bloated or you cry more easily.

You may also feel discomfort or pain in your lower abdomen or back. The pain may last for some or all of your period. There is help if painful periods are a problem, so don't suffer in silence. Find out more about treatment for painful periods.

Premenstrual syndrome (PMS)

Premenstrual syndrome (PMS, sometimes called premenstrual tension or PMT) is the name for a set of physical, psychological and emotional symptoms that can appear in the days leading up to a woman's period. PMS doesn't affect every woman who has periods. If it does affect you, symptoms can include:

  • feeling irritable and bad-tempered
  • mood swings
  • fluid retention and feeling bloated

Usually if you get these symptoms they'll improve when your period starts and disappear a few days afterwards.

Changes in your periods

Women's periods can change, for example they may get longer or lighter. This doesn’t necessarily mean there's a serious problem, but it does need to be checked. You can go to a doctor, women's clinic or contraceptive clinic. Find services in your area, including doctors.

Any bleeding between your periods, bleeding after having sex or after the menopause needs to be checked by a doctor. Bleeding like this can be due to infection, abnormalities in the cervix or, more rarely, cancer. Find out more about [what causes bleeding between periods].

If you miss a period and you've had sex, you could be pregnant. Find out by taking a pregnancy test. If you're not pregnant and you miss two or three periods, see a doctor.

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Period complications

Some women have problems with their periods. Don't assume that you have to put up with it. Talk to your doctor as there may be treatments that can help.

Period problems can include:

  • heavy periods (menorrhagia)
  • painful periods (dysmenorrhoea)
  • irregular periods
  • not having any periods at all (amenorrhoea)

Heavy periods (menorrhagia)

The amount of blood lost during a period varies from woman to woman. But if your periods are so heavy that you feel they are disrupting your life and making you feel miserable, see your doctor. There is treatment that can help.

You might have heavy periods if:

  • you feel that you are using an unusually high number of tampons or sanitary towels
  • blood leaks through to your clothes
  • you need to use a sanitary towel and a tampon to prevent leaking

For more information, see:

Painful periods (dysmenorrhoea)

Most women experience painful periods at some point in their lifetime. The pain can be in your lower abdomen (tummy), pelvis, lower back, thighs and vagina shortly before and during your period.

The pain might be slight or very severe. If the pain is bad and you find it hard to cope, talk to your doctor.

Painkillers such as non-steroidal anti-inflammatory drugs (NSAIDs) can be used to treat painful periods.

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Irregular periods

Periods can last between two and eight days, and the menstrual cycle (the time from the start of one period to the day before the next period) normally lasts from 24 to 35 days.

If you have irregular periods, the gaps between your periods will vary, as will the amount of blood you lose (how heavy your periods are) and how long your period lasts.

There are many possible causes of irregular periods, and treatment will depend on the underlying cause. Possible treatments include changing your method of contraception, relaxation classes and counselling.

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Absent periods (amenorrhoea)

Sometimes a woman may stop having periods altogether. This is known as absent periods, or amenorrhoea. Usually this means that no eggs are produced. If you don't produce eggs (ovulate), you can't get pregnant.

There are many possible causes of absent periods, including severe stress, extreme weight loss, various medications and polycystic ovary syndrome. Treating the underlying cause often brings your periods back.

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