A period is when blood leaves the womb through the vagina. This happens about every 28 days. Girls most commonly start their periods around the age of 12.
It is normal for a female to not have any periods under the following circumstances:
- When a girl has not yet gone through puberty.
- When a woman is pregnant, breastfeeding or going through the menopause (usually at the age of 40 or older).
- When a woman has had a hysterectomy (operation to remove the womb).
However, an absence of periods when they should normally occur, known as amenorrhoea, may indicate an underlying health problem or severe weight loss (see Causes). When there is amenorrhoea, ovulation (the release of eggs) does not occur.
Amenorrhoea may be categorised as either primary or secondary.
Primary amenorrhoea
Primary amenorrhoea is the failure to start your periods. It is regarded as abnormal if:
- you have not started sexual physical development and periods by the age of 14, or
- you have not started your periods by the age of 16 but have normal sexual physical characteristics for your age (see Diagnosis)
Primary amenorrhoea affects only about three girls in every 1,000.
Secondary amenorrhoea
Secondary amenorrhoea is defined as the absence of periods for six consecutive months in a woman who previously had regular periods.
Secondary amenorrhoea suggests that there is a gynaecological disorder or a more general cause, such as being severely underweight. It affects about three females in every 100.
Up to 50% of competitive long-distance runners (those who run 80 miles or more a week) and up to 44% of professional ballet dancers have amenorrhoea (see Causes).
Outlook
There is usually an underlying cause for amenorrhoea that can be treated. Treating it often brings back your periods.
