Menstruation

Menstruation is commonly called a period, and is what adolescent girls and women of child-bearing age usually experience as a flow of blood from the vagina.

It is caused by a build-up of blood on the lining of the womb (uterus), in response to hormones. Periods usually last between 3–7 days, with the blood flow usually starting heavy and getting lighter during this time.

Most girls or women get their period once a month, but anywhere between every 3 and 6 weeks is normal.

Your first period

Girls often get their first period at 12 or 13, but this can happen earlier or later. When your period starts, it may be irregular at first. This means you might not know when to expect your next period. If your period has not started by the age of 16, see a health professional.

What causes periods?

Periods are triggered by hormones that send a message to the uterus to prepare for a possible pregnancy. These hormones make the lining of the uterus thick so that if an egg is fertilised by male sperm, it can implant safely in the uterus wall.

If the egg isn't fertilised and no pregnancy occurs, the uterus sheds the thick lining. The blood that leaves the vagina during the period is due to the uterus lining coming away.

This process continues to happen monthly until you reach your late 40s to early 50s. When your hormones decrease and your periods stop, this is called menopause.

Common menstrual problems

• Premenstrual Syndrome (PMS)—hormonal changes in the body where women experience headaches, fatigue, irritability and fluid retention. Treatment options include exercise and dietary changes.
• Dysmenorrhoea—painful periods. Treatment options include painkillers and the oral contraceptive pill.
• Menorrhagia—heavy menstrual flow. If left untreated, this can cause anaemia. Treatment options include oral contraceptives to regulate the flow.
• Amenorrhoea—absence of menstrual periods. This is considered abnormal, except during pre-puberty, pregnancy, lactation and menopause. Possible causes include low or high body weight and excessive exercise.
• Fibroids—growths or benign tumours that form inside the uterus. Fibroids often cause no problems, but may occasionally be associated with infertility, miscarriage and premature labour. Possible problems include heavy, lengthy and painful periods. Treatment depends on the size, number and location of the fibroids, but may include drugs and surgery.
• Late period—can be due to pregnancy, varying lengths of a menstrual cycle, stress, excessive exercise, excessive weight loss or change of routine.
• Unusual bleeding—heavy, irregular or unpredictable periods, bleeding between periods or after sex. Can be due to a number of causes including sexually transmissible infections, uterine fibroids or hormonal disturbances.
• Endometriosis—tissue similar to that which normally lines the uterus grows in other parts of the body

Read more about menstrual problems.

More information

See your local doctor, family planning clinic or sexual health clinic.

You can also read more from True relationships and reproductive health.