Endometriosis is characterized by tissue that normally lines the uterus abnormally growing outside the uterus. The lining of the uterus — or endometrium — thickens in response to hormones such as estrogen as part of the female reproductive cycle, in preparation for a potential pregnancy. If no pregnancy occurs, the tissue breaks down and is shed with menstruation.

Abnormal growths, or endometrial lesions, that develop outside the uterus also respond to estrogen but cannot be removed in the same way. Their presence often leads to pain, infertility, and may scar internal organs.

Who does endometriosis affect?

Endometriosis can affect women regardless of racial or ethnic background, and typically occurs in those of childbearing age (usually, 20s and 30s), or in women between the menarche — the first menstrual cycle — and the onset of menopause. As such, endometriosis patients can range in age from 15 to 49, but patients as young as 11 are known.

The painful symptoms of endometriosis may ease following menopause in some women.

How common is endometriosis?

Endometriosis is estimated to affect around 1 in 10 women of reproductive age. For example, the U.S.-based ENDO study, published in the journal Fertility and Sterility, found that 11 percent of 131 women in a population group had endometriosis (diagnosed by pelvic MRI).

Endometriosis may be present in around 30 to 50 percent of women with infertility, as not having given birth is a disease risk factor and infertility is a common disease complication.

According to a study carried out in Israel and published in BJOG, endometriosis may be most prevalent in women ages 40 to 44.

The disease is rare in women who have already been through menopause, but may still develop. It is estimated to occur in around 2 to 5 percent of postmenopausal women, though this may include previously undiagnosed cases.

Are women diagnosed correctly?

Many endometriosis patients experience a significant delay between the onset of symptoms and a diagnosis of endometriosis. A study published in Fertility and Sterility estimated a delay of about 6.7 years until a surgical diagnosis based on the experiences of 1,418 women in 10 countries.

A survey conducted by Endometriosis UK in 2011 suggested that it takes around 7.5 years, on average, to be diagnosed with the condition.

Many cases of endometriosis are also believed to go undiagnosed, possibly because patients do not seek clinical care or because they are misdiagnosed. This means that the prevalence of endometriosis may be higher than currently thought.


Endometriosis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.