What is endometriosis?
Endometriosis, pronounced end-o-me-tree-oh-sis (or just endo) is a progressive, chronic condition where cells similar to those that line the uterus (the endometrium) are found in other parts of the body.
Studies suggest that endometriosis affects 1 in 10 women of reproductive age, with an estimated 176 million women worldwide having the condition.
What causes endometriosis?
We don't really know what causes endometriosis, and possible causes or factors may be different from person to person.
- Family history: women who have a close relative with the condition are up to 7-10 times more likely to get endometriosis. Also, it is common with twins that both may get endometriosis, particularly if they are identical twins.
- Retrograde (backwards) menstruation: When a woman has a period, the blood flows out of the vagina, but also backwards along the fallopian tubes into the pelvis. In 90% of women, the blood, which will contain endometrial cells is absorbed or broken down and causes no symptoms; however, in women with endometriosis this endometrial tissue starts to grow.
- Metaplasia: the conversion of the normal pelvic tissue into endometriosis.
Other possible factors that may have a role in causing endometriosis are:
- having first pregnancy at an older age
- heavy bleeding during periods and periods lasting longer than five days
- first period before 11 years of age
- regularly having less than 27 days between periods, or having shorter regular cycles
- changes in the immune cells
- low body weight
- alcohol use
The endometrial cells:
- are found on organs in the pelvis
- may start to grow and form patches or nodules on pelvic organs or on the peritoneum (the inside lining of the abdomen and pelvis, see image)
- have the same cyclical/menstrual changes outside the uterus as inside the uterus
- may bleed at the same time as your period (menstruation)
Factors that may lower the risk of getting endometriosis are:
- how many children you have – the chance of getting endometriosis may lower with each pregnancy (this may be related to the hormone progesterone during pregnancy)
- younger age of first pregnancy
- breastfeeding for a longer period
- regular exercise of more than four hours per week (this may also help with pelvic pain for endometriosis)
There may be different forms or types of endometriosis
- Superficial peritoneal patches (surface lining patches or plaques)
- Deep infiltrating endometriosis, in which endometriosis causes scarring and nodules which can grow into nearby organs, such as the bladder, bowel and ovary. In the ovary it causes a 'chocolate cyst' or endometrioma
- Adenomyosis, whereby the endometrial cells grow inside the muscle of the uterus
- Outside the pelvis - this is rare
- Upper abdomen eg, on the diaphragm
- In the liver, nose, eye
- Abdominal wall, often associated with previous operation scarring
- Adolescent endometriosis, which may have different causes
How do you know if you have endometriosis?
The symptoms vary from woman to woman. Some women have many symptoms and severe pain, whereas others have no symptoms. About a third of women with endometriosis discover they have it because they have not been able to become pregnant, or because endometriosis is found during an operation for another reason.
The type of symptoms and their severity are likely to be related to the location of the endometrial tissue rather than the amount of endometrial cells growing.
About three out of four women with endometriosis have pelvic pain and/or painful periods.
In the early stages of the disease, one or two mild symptoms may be felt for the first day or two of a period. Later, as the condition continues, symptoms may get worse for more days of the month, both during and before the period.
In women over the age of 25, endometriosis can make it difficult to get pregnant. This may be because the endometrial cells release chemicals that cause inflammation that:
- interfere with the ability to get pregnant
- affect the development of the embryo in its early stages
In moderate to severe cases, the scarring caused by the endometrial cells may interfere with the release of an egg (ovulation), due to damage or blockage. The damage can also prevent the journey of an egg along the fallopian tube and/or the sperm from reaching the egg, causing problems with fertility.
Symptoms you may experience
Pain is a key symptom of this condition and is not related to how severe the disease is, but to the location of endometrial tissue.
|Bladder and bowel problems||
Increase abdominal bloating, with or without pain at the time of the period
|Tiredness||Tiredness or lack of energy, especially around the time of the period|
|Mood changes||Anxiety and depression due to ongoing pain|
|Reduced quality of life||Taking days off work, study or school because of an inability to function normally|
Pelvic floor muscle spasm or tightening occuring because of fear of pain previously experienced with intercourse or tampon use
Symptoms during pregnancy
In many cases, the symptoms of endometriosis appear to go away with pregnancy. This is thought to be because pregnancy hormones cause the endometriosis to reduce. After the baby is born the effects of endometriosis are unclear. In a small study of 23 women, the endometrial lesions worsened in the first three months of pregnancy, but improved as the pregnancy continued. Complications of endometriosis during pregnancy are rare.
Symptoms during menopause
Usually, endometriosis does go away after menopause. It may return with the use of hormone replacement therapy (HRT), but this is rare. Even more rarely, it can return for no reason.
When to get help
Get help when period pain is stopping normal daily activities. For example:
- missing work, school or recreational activities
- when medicines used for period pain don't help reduce the pain
- when you need to stay in bed due to pain
- when symptoms are getting worse
- when you feel upset by your symptoms
- when your ability to cope mentally decreases
Ahn SH, Monsanto SP et al, Pathophysiology and Immune Dysfunction in Endometriosis. Biomed Research International. 2015; ID 795976, 1-12
Carvalho L, Podgaec S, Bellodi-Privato M, Falcone T, Abrão MS. Role of eutopic endometrium in pelvic endometriosis. J Minim Invasive Gynecol. 2011; 18:419-27
Leone Roberti Maggiore U, Ferrero S, Mangili G, Bergamini A, Inversetti A, Giorgione V, Vigano P, Candiani M. A systematic review on endometriosis during pregnancy: diagnosis, misdiagnosis, complications and outcomes. Hum Reprod Update. 2016; 22:70–103.
Riazi H et al, Clinical diagnosis of pelvic endometriosis: a scoping review. BMC Women's Health. 2015;15: (39) 1-12
Last updated 11 September 2018 — Last reviewed 06 October 2016
This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at October 2016.