Incidence

Prevalence of endometriosis in the general population is unknown since diagnosis requires laparoscopic conformation. The estimated prevalence of the disease is thought to be between 1.5% to 6.2% (1).

• however, the true prevalence is difficult to estimate because of differences in diagnostic thresholds and criteria between studies, and in variations in childbearing age between populations (1).
• prevalence of the disease varies by geography and race with the highest prevalence seen in Japanese women (2)

Ectopic endometrial tissue is found in 10-15% of all women in the reproductive years (1).

• the incidence is 40-60% in women with dysmenorrhoea and 20-30% in those with subfertility (1).
• endometriosis is seen in about 6% of women undergoing sterilisation and as many as 25% of women undergoing hysterectomy (3).

However as the use of laparoscopy has become more widespread, these associations are seen to be less certain.

Endometriosis tends to regress during pregnancy, due to the predominance of progesterone, and after the menopause in women not on oestrogen replacement therapy. Combined oral contraceptive pill users have a lower incidence of endometriosis.

Heritability studies have shown that the risk of endometriosis is higher in women with affected first degree relatives (4).

Reference:

• (1) Clinical Evidence 2010. Endometriosis
• (2) Amer S. Endometriosis. Obstetrics, Gynaecology and Reproductive Medicine 2008;18(5):126-133 .
• (3) NHS Evidence – women’s health. Endometriosis. Annual Evidence Update March 2010
• (4) Farquhar C. Endometriosis. BMJ 2007;334:249-253