All about periods

1. What is menstruation?

  • Menstruation (or a period) is the regular shedding of blood and the lining of the womb due to cyclical hormonal changes in a woman's body.                                   
  • When a baby girl is born, her ovaries already have millions of immature ova (eggs). At puberty, tens of them will start growing under hormonal stimulation once a month. Generally, only one ovum reaches maturity in the ovary and is released into the womb (known as ovulation) every cycle.
  • At the same time, the lining of the womb becomes thicker in preparation for pregnancy. If the ovum is not fertilised, it will be passed through the vagina together with the extra tissue lining of the womb as menstrual blood. Then, another menstrual cycle starts again.

2. At what age does a girl begin to have periods? At what age do periods stop?

  • Most girls begin to have their period at around age of 11-12. For most women, natural menopause takes place between the ages of 45-55. At this stage, periods stop permanently (menopause) and the women are no longer fertile.

3. Must I have a period every month?

  • No, not all women have a period every month. A woman's cycle may vary depending on her condition.
  • A menstrual cycle may last for 21 - 35 days. The length of a cycle is defined as the number of the days between the first day of a period to the first day of the next period.

    For example:

    First day of last period: 1st October
    First day of current period: 29th October
    Cycle length: 28 days

  • Irregular periods can occur in girls who have just started menstruation and in women approaching menopause.
  • Certain conditions can be associated with hormonal imbalance, which in turn causes irregular periods. These include:
    • overweight or underweight
    • Eating disorders (e.g. anorexia nervosa)
    • Vigorous exercise
    • Stress
    • Certain medications (e.g. contraceptive injections)
    • Drug abuse
    • Breastfeeding
    • Chronic diseases, hormonal disorders (e.g. polycystic ovary syndrome, thyroid disease etc.)
    • Conditions which affect ovarian function
  • Vaginal bleeding in-between periods may be due to abnormality in the lining of the womb, polyps, infection of the cervix or vagina, or due to cancer of the cervix etc. This can sometimes be confused with having 'irregular periods'.

The possibility of pregnancy must be considered in any sexually active women. Please seek advice from your health care providers if you have missed your period.

4. Have I got heavy periods?

  • Heavy periods mean increase in severity or duration of menstrual bleeding.
  • You may have heavy periods if:
    • Your period lasts longer than 7 days (most women have periods lasting 2 - 7 days)
    • You need to change long and super-absorbent pads once every 1 - 2 hours
    • You are passing large blood clots
    • You have floods (i.e. suddenly pass a large amount of blood which soaks through your underwear and clothes)
    • You need to get up frequently at night to change pads
    • You bleed onto your bed sheets whilst sleeping, even you are useing a pad / tampon
    • Your heavy period is affecting your work, family life and social life
    • You feel dizzy, shortness of breath and tired during and after your period

5. What are period pains?

  • Period pains often start shortly before or at the onset of the period. Generally a mild to severe pain is felt in the lower abdomen.
  • Pains are usually worse when there is heavy bleeding.
  • Pains can be associated with stomach upset such as vomiting or passing loose stools.
  • There are 2 types of period pains:

Not caused by a medical condition

Caused by an underlying condition

  • Usually occurs in young women shortly after they start having periods
  • Pain is less or even disappears as the woman gets older or has given birth
  • Can be caused by conditions such as endometriosis, pelvic infection, the use of intrauterine contraceptive device etc.
  • Lasts for 1-3 days
  • Pain can occur at any time of the menstrual cycle
  • May have foul smelling vaginal discharge or fever
  • May feel pain during sexual intercourse
  • Pain is relieved by applying hot compress or taking simple painkillers
  • Women who exercise regularly often have less period pains
  • Pain may not be relieved by taking simple painkillers
  • Treatment of the underlying cause helps to reduce the pain

See your doctor if you have any of the followings:

  • You are 16 years old and your periods have not started
  • Your periods have suddenly become irregular
  • Vaginal bleeding in between periods
  • Vaginal bleeding after sexual intercourse
  • Vaginal bleeding after your periods have stopped for over a year
  • Period pains which start at or after 40 years old
  • Menstrual cycle is shorter than 21 days
  • Heavy periods (refer to question 4)
  • Severe painful periods / abdominal pain
  • Your periods have stopped for over a year but you are under 45 years old

Please seek advice from health care professionals if you have any queries.

(Content revised 05/2014)