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Periods - the facts

periods; menstruation; menstrual; cycle; premenstrual; tension; blood; tampons; sanitary; napkins; pads; bleeding; uterus; vagina; painful; dysmenorrhoea;


Having a period (or menstruating) is a normal and natural part of being a woman. Girls usually have their first period about a year after the first signs of puberty (when they start to get taller and breasts start to grow), but the time this happens can vary a lot.

Have a look at the topic 'Periods - what to do' for more information.

The 'Periods - what to do' topic contains information about

The menstrual cycle and menstrual periods

Having your first period tells you that your body has changed, and you are becoming a woman who will be able to have a baby, if and when you want to. The period (the days that you lose blood through the vagina) is part of a 'cycle' of hormone and body changes.

  • During each cycle, the lining of the inside of your uterus (womb) gets thicker, so that if the egg (ovum), which is released from your ovary each cycle, is fertilised by a sperm, the uterus is ready to provide a place for the baby to grow.
  • A period is when the lining separates from the rest of the uterus because it is not needed for this egg to grow. The old lining is 'lost' and the uterus gets ready to make a new lining for the next egg.
  • The 'loss' is mostly blood, which can be bright red, dark red or dark brown, and sometimes has some clots (dark lumps of blood) in it.
  • How long a period lasts (often between about 4 and 7 days) and the time between periods varies (often between about 3 and 5 weeks) for different women.

The menstrual cycle

When do periods start?

The first period happens for many girls between the ages of 12 to 14 years, but quite often it is earlier (from as early as 9 years old) or later (up to 16 years).

  • Girls start having periods at different times depending on how quickly they are developing.
  • If a girl has not had her first period by the time she is 16, this is still probably normal, but it would be worth checking with a doctor.
  • Once you get your period, it may take quite a long time for your body to settle into a regular pattern – maybe up to a year – but most women eventually do get into a regular cycle.
  • It is a good idea to keep track of when your period is due, maybe on a calendar or in your diary.
  • If the pattern changes and you have been sexually active, it may mean you are pregnant. It could also mean there are other reasons - such as losing too much weight or exercising too much.

What happens in the monthly menstrual cycle?

  • On average, a cycle lasts about 28 days, but it’s quite normal to have a shorter or longer cycle. So your cycle will probably be normal for you even if it is 21 days long, or 35 days!
  • ‘Day 1’ of a cycle is the first day of bleeding, the first day of a period. This bleeding is called menstruation.
    • On average, when periods have become regular, this bleeding lasts for about 5 days.
    • For many young women in the first year or so of having periods, the bleeding can last for longer (7 to 10 days is fairly common).
    • Usually bleeding is heaviest on the first or second days.
    • Many young women get quite a lot of crampy pain in their lower tummy just before and during the first day of their period.
  • As soon as one period finishes, the lining of the uterus starts to grow again and becomes thicker ready for another egg (ovum). It continues to get thicker until a couple of days before the next period starts (unless the ovum has been fertilised and the woman is pregnant).
  • About 12-16 days before your next period, an egg is released from your ovary. This is called ovulation. (A few women feel a sharp pain in the side of their tummy at this time.)
  • This egg travels along the fallopian tube from the ovary to the uterus. An egg survives for only about 24 hours if it is not fertilised by a sperm.
  • If fertilisation does not happen, hormone levels drop, and you have a period. And then the whole cycle continues.

How much blood is lost?

  • The loss is mostly blood, but also contains some mucus and other tissues from the lining of the uterus.
  • Sometimes it seems like a lot of blood, but it is usually less than 100ml. If you weigh 50kg you will have about 3.5 litres of blood in your body, so losing 100ml with a period will not cause health problems. The blood that you lose will be quickly replaced by the blood-forming cells in your bone marrow.
  • Sometimes a woman will have very heavy periods, and lose a lot of blood. She may have a lot of clots in the blood that is lost. If too much blood is lost she can become anaemic (not enough red blood cells). She may need to have extra iron in her diet (eg. from foods or iron tablets) to help her blood form cells to replace all that lost blood. It's really important to see your doctor if you are having heavy periods.

Symptoms before a period

Many women experience some symptoms before a period (called pre-menstrual symptoms) due to all the hormone changes that are happening. They can include:

  • Feeling bloated and heavy.
  • Cramping pains around the lower abdomen, in the legs or sometimes in the lower back.
  • Getting more pimples than usual.
  • Feeling tense, irritable, sensitive, emotional, tired.
  • Breasts becoming a little bigger and tender.
  • Hair becoming more greasy.

Your doctor will be able to give you some ideas to help with managing this if you are finding it a problem, and may sometimes suggest some medication.

Will other people know you have your period?

No way! Do not fear – despite sometimes feeling like someone can see a pad, or notice that you are ‘different’ at this time of the month, people will not notice that you are having a period.

At any one time about 20% of all young adult women will be having a period. Can you pick which other students are having a period? Or which teachers are having their period? Do you know when your mother is having her period, unless she tells you?

Only you will know, unless you tell someone yourself.

Periods - what to do

Have a look at the topic Periods - what to do for more information.

Want to know more?

Better Health Channel (Victorian Government) 

There is a lot of information on the TeensHealth.org website - search 'periods'. 

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The information on this site should not be used as an alternative to professional care. If you have a particular problem, see a doctor or other health professional.
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