Endometriosis

What is endometriosis?

Endometriosis is not only a gynecological condition. It is a chronic and complex disease that involves the whole body and can affect a woman at every stage of life, even after the menopause.

In endometriosis, tissue similar to the inner lining of the uterus (the endometrium) grows outside the uterus. It is usually found in the pelvis: on the peritoneum, on the ovaries, on the ligaments of the uterus, and sometimes on the bowel or the bladder. Rarely, it also appears outside the abdomen, for example on the diaphragm or in surgical scars.

This tissue responds to the hormones of the cycle, mainly to estrogen. It causes inflammation, pain and adhesions, where organs stick together. That is why the symptoms often get worse shortly before and during the period.

Endometriosis affects about 10-12% of women of reproductive age and is much more common in women who have difficulty getting pregnant. Although it is so common, it is often diagnosed late. According to a 2024 systematic review, 5 to 12 years pass on average between the first symptoms and the diagnosis. A common reason is that period pain is seen as “normal”, by women themselves and also by doctors.

This delay has consequences. When pain goes untreated for years, the nervous system becomes more sensitive to pain (central sensitization). The pain then becomes chronic and is harder to treat once treatment does start. In some women the disease spreads, with cysts on the ovaries, adhesions or deep endometriosis. This can reduce ovarian reserve and fertility. Years without a diagnosis also mean missed days at school and work, and a burden on mental health and relationships.

This is why early diagnosis and early treatment matter so much. Some women have a higher risk and need special attention, starting in puberty. When a mother or sister has endometriosis, the risk is several times higher. Girls with severe period pain that leads to missed school, or that does not respond to painkillers and the combined pill, also have a higher risk. The same applies to women with an early first period, short cycles or increased bleeding during periods, and to women with abnormalities of the uterus that block the flow of menstrual blood. In these women, the doctor can start treatment based on the symptoms, without waiting for surgical confirmation.

Why does it develop?

The exact cause is not known. The most widely accepted theory is that during the period some of the blood and tissue of the lining of the uterus flows backwards, through the fallopian tubes, into the abdomen. But this happens in many women, while only some develop endometriosis. Heredity, the immune system and estrogen seem to play a role. There is no proven way to prevent it.

Is it more than pain and infertility?

Endometriosis does not only mean pain or difficulty getting pregnant. Studies show that women with endometriosis have a higher risk of heart disease, as well as of autoimmune and rheumatic diseases. The chronic inflammation that comes with the disease is thought to be one of the reasons.

There is also a higher risk of certain types of cancer, mainly certain forms of ovarian cancer. The absolute risk for each woman remains low, and according to the guidelines no special screening is needed beyond the usual, unless there are additional risk factors such as a family history. Knowing about these risks is still important for long-term follow-up.

What are the symptoms?

The most typical symptom is severe period pain that often does not improve with simple painkillers and affects work, school or daily life. Many women also have pain in the abdomen or lower back outside the period, pain during or after sex, pain when passing urine or opening the bowels, mainly during the period, and severe tiredness. Some women have no symptoms at all, and the endometriosis is found by chance.

Chronic pain affects mood, sleep, relationships and quality of life. A symptom diary, in which a woman notes her pain and how it relates to her cycle, helps a lot with diagnosis and follow-up.

Adenomyosis can cause similar symptoms. In adenomyosis, the tissue of the lining of the uterus grows into the muscle wall of the uterus. It usually causes severe pain and increased bleeding during periods. In the past, adenomyosis was seen as “endometriosis of the uterus”. Today it is considered a separate disease. Many women with endometriosis also have adenomyosis. Having both conditions at the same time is a real challenge. The two diseases reinforce each other and can worsen both quality of life and fertility. In addition, adenomyosis often responds poorly to the usual medicines for endometriosis. Its treatment therefore requires specialized expertise. More in the article “Adenomyosis”.

What forms of endometriosis are there?

Endometriosis has three main forms. The superficial form involves small lesions on the peritoneum. Endometriomas are cysts on the ovaries, also known as “chocolate cysts”. The deep form grows deeper into the tissues and can involve the bowel, the bladder or the ligaments of the uterus.

The extent of the disease does not always match the strength of the pain. Small lesions can cause severe pain, while extensive disease can cause few symptoms.

How is the diagnosis made?

The diagnosis starts with the history and the symptoms. This is followed by a gynecological examination and a vaginal ultrasound, and in some cases an MRI scan. A normal ultrasound does not rule out endometriosis, because small superficial lesions are often not visible.

The final diagnosis of endometriosis is surgical, by keyhole surgery (laparoscopy) with a tissue examination. According to the latest guidelines, however, laparoscopy is no longer needed to suspect endometriosis or to start treatment. Treatment can start based on the symptoms and the findings of the examination. In addition, a laparoscopy without visible lesions does not rule out endometriosis, because small or atypical lesions can be missed. Blood tests, such as the CA-125 marker, are not suitable for the diagnosis.

What does conservative treatment involve?

Endometriosis cannot be cured for good, but the symptoms can be controlled effectively and the disease can be kept in check. Treatment with medication, hormonal or non-hormonal, is the first choice for most women.

Hormonal treatments reduce the effect of estrogen and “calm” the endometriosis lesions. Combined contraceptives and progestin-only treatments, as a pill, a hormonal IUD or an implant, are the most common first-line options. They are effective, have limited side effects and can be used for a long time. When they are not enough, there are medicines that lower estrogen strongly. Because they cause menopausal symptoms and bone loss, the doctor usually adds a small dose of hormones. In young women they are only a second choice. Hormonal treatments control the symptoms for as long as they are taken. Stopping them can lead to a flare-up of the disease, and the symptoms often come back. That is why treatment is usually long-term and needs regular review. More in the article “Hormonal treatment of endometriosis”.

There are also non-hormonal treatments that can help, mainly alongside other treatment. Some women also look for help in complementary treatments, and some of these have been studied in endometriosis. More in the article “Non-hormonal and complementary treatments for endometriosis”.

When is surgery the right choice?

Surgery is the better choice in specific cases, when the benefit is greater than the possible risks. Removing the endometriosis lesions by keyhole surgery usually improves the pain. However, the improvement may be partial or temporary, and endometriosis often comes back.

The most important risk concerns the ovaries. Removing cysts from the ovaries can reduce the number of eggs, shorten a woman's reproductive years and raise the risk of premature ovarian insufficiency or early menopause. That is why the decision to operate, especially to operate again, needs careful weighing. Deep endometriosis is best treated in specialized centers.

A hysterectomy is only considered when other treatments have not helped and there is no wish for another pregnancy.

How does endometriosis affect fertility and pregnancy?

Most women with endometriosis can become pregnant, many without any treatment. But pregnancy does not “cure” endometriosis.

Egg quality in endometriosis is debated in the literature, and some studies find no difference. In a 2024 meta-analysis of 31 studies, women with endometriomas who had IVF had similar rates of fertilization and blastocyst development as other women. However, they had fewer mature eggs and fewer top-quality embryos. Overall, data from IVF cycles tend to show poorer egg quality. A 2017 systematic review showed that eggs from women with endometriosis more often fail to mature in the laboratory, more often have changes in their shape and contain fewer mitochondria. In an egg donation study, embryos from eggs of women with endometriosis had a lower implantation rate. In contrast, women with endometriosis who received eggs from donors without the disease had the same results as other recipients. This shows that the disease also affects the egg itself.

Hormonal treatments do not improve fertility, and a woman stops them when she wants to become pregnant. In some cases, surgical removal of the lesions can increase the chance of a natural pregnancy, but the possible damage to the ovaries must be weighed. Assisted reproduction is safe for women with endometriosis and does not make the disease worse. The choice depends on age, ovarian reserve, the function of the fallopian tubes, male factors and previous attempts. More in the article “Endometriosis and infertility”.

Endometriosis also affects pregnancy itself. In a meta-analysis of 24 studies with almost two million women, women with endometriosis had about a 1.8 times higher risk of miscarriage, a 1.6 times higher risk of preterm birth and a 3 times higher risk of placenta previa. The risk of a baby that is small for gestational age and of a cesarean section was also higher. A more recent meta-analysis also found a higher risk of high blood pressure in pregnancy, pre-eclampsia and placental abruption. For this reason, the pregnancy of a woman with endometriosis needs an individual approach. Depending on her history, the doctor may manage it as a high-risk pregnancy, with closer monitoring.

How does endometriosis affect quality of life?

The quality of life of women with endometriosis is often clearly reduced. Pain, fear of complications (especially for fertility), hormonal imbalance and the inflammatory nature of the disease create a vicious circle. In this circle, pain, tiredness, a general feeling of being unwell, emotional distress, mental health problems and lack of sleep make each other worse.

The data confirm this. About 50% of women with endometriosis report frequent fatigue, twice the rate in women without the disease. In a 2022 meta-analysis, women with endometriosis had clearly more symptoms of depression and anxiety than healthy women. These symptoms were closely linked to chronic pain, sleep quality and fatigue. Sleep problems are common and, in turn, make the pain worse.

For this reason, although hormonal treatment is important for controlling the course of endometriosis, it cannot always be the only option. Hormonal medicines can worsen several of the psychosomatic symptoms of the disease, such as mood, sleep and sexual desire. The doctor must listen to and respect the woman's needs and wishes, even beyond what the guidelines say.

Can endometriosis start in puberty?

Endometriosis can start as early as puberty. Severe period pain that leads to missing school, pain outside the period, or pain in the bowel and bladder needs attention and should not be seen simply as “normal period pain”. The doctor should recognize these girls early and treat them as a high-risk group for endometriosis. It is just as important to reduce the pain, in order to lower the risk of central sensitization.

Treatment can be hormonal, but it must take into account the hormonal and metabolic changes of puberty and must be individual. Good communication with the girl and her parents ensures the best result.

What happens in the menopause?

Endometriosis does not always end with the menopause. The symptoms usually fade, but they can continue in some women. Women with endometriosis need careful follow-up in the menopause, whether it comes naturally or is caused by surgery or medication.

Menopausal hormone replacement therapy can be used. Women with endometriosis need combined hormone replacement therapy with estrogen and progesterone, even after a hysterectomy, because estrogen alone can reactivate remaining lesions. Hormone replacement therapy is especially important for women who entered the menopause early after surgery, to protect the bones and the heart.

The practice's approach

Sources: Becker CM et al., ESHRE guideline: endometriosis, Human Reproduction Open 2022. National Institute for Health and Care Excellence (NICE), Endometriosis: diagnosis and management (NG73). De Corte et al., BJOG 2024 (diagnostic delay). Mu et al., Circulation 2016 (cardiovascular risk). Shigesi et al., Human Reproduction Update 2019 (autoimmune diseases). Kvaskoff et al., Human Reproduction Update 2021 (cancer risk). Zullo et al., Fertility and Sterility 2017 and Breintoft et al., Journal of Clinical Medicine 2021 (pregnancy complications). Ramin-Wright et al., Human Reproduction 2018 (fatigue). van Barneveld et al., Journal of Women's Health 2022 (depression and anxiety). Qi Q et al., Update on the pathogenesis of endometriosis-related infertility based on contemporary evidence, Frontiers in Endocrinology 2025. Sanchez AM et al., Is the oocyte quality affected by endometriosis? A review of the literature, Journal of Ovarian Research 2017. Gayete-Lafuente S et al., Indirect markers of oocyte quality in patients with ovarian endometriosis undergoing IVF/ICSI: a systematic review and meta-analysis, Reproductive BioMedicine Online 2024. Simón C et al., Outcome of patients with endometriosis in assisted reproduction: results from in-vitro fertilization and oocyte donation, Human Reproduction 1994.