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Irregular periods

Your menstrual cycle begins on the first day of your menstruation and continues up to, but not including, the first day of your next period. Women’s cycles range from 21-40 days or more, with an average of around 28 days.

The length of your cycle may change from month to month. Periods usually last between two to seven days and blood loss varies from light to heavy and bright red to dark brown.

Any alteration in what you consider to be your normal cycle can be a cause for concern. Variations may mean you have a period more often or less often than is normal for you or you may not have a period at all. You may also bleed more or less than normal, and the length of your period may also change.

The absence of periods (or amenorrhoea) usually occurs because an egg is not produced in the ovaries. The most common causes of absent periods are:

There are several other factors that may cause your periods to stop or to become lighter or less frequent, such as:

  • menopause
  • excessive exercise
  • being underweight or excessive dieting
  • feeling upset or stressed
  • severe long term illness
  • a hormonal imbalance
  • a thyroid disorder
  • stopping or starting the contraceptive pill or other hormonal contraception (including the patch, IUS (Mirena) coil, implant (rods) or injection)
  • some medicines
  • disorders of the womb or ovaries.

Experiencing changes in the frequency or duration of periods is common in most women at some point in their lives. Any treatment or investigation of irregular or light periods will depend on the likely cause.There will, for example, be no need for treatment if you are nearing the menopause as irregular periods are common during this time.

Not sure what to do next?

If you are still concerned about your irregular periods, check your symptoms with healthdirect’s online Symptom Checker to get advice on when to seek medical attention.

The Symptom Checker guides you to the next appropriate healthcare steps, whether it’s self care, talking to a health professional, going to a hospital or calling triple zero (000).

Last reviewed: July 2015

Need more information?

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The start of the third week since the beginning of your last menstrual cycle (15-21 days) is the first week of your babys growth. If you have an average-length (28 day) menstrual cycle, your egg and your partners sperm will most likely fuse together to conceive your new baby on day 15. The fertilised egg, known as a zygote, then travels through your fallopian tubes and into your womb where it implants to continue its growth. Although women are unaware they are pregnant at this stage, week 3 of pregnancy is a time of rapid changes for both mum and baby.

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