Endometriosis and Fertility: Understanding the Condition and Your Treatment Options

Endometriosis affects approximately 190 million people worldwide — around 10% of women and girls of reproductive age. Yet despite its prevalence, it remains one of the most misunderstood, underdiagnosed, and undertreated conditions in medicine. On average, women in Europe wait 7–10 years from the onset of symptoms to receive a correct diagnosis. For those hoping to start or grow their families, this diagnostic delay can have profound implications for fertility.

In this comprehensive guide, we explore what endometriosis is, how it affects fertility, the diagnostic journey, and the full range of treatment and reproductive options available today. Whether you've recently been diagnosed, suspect you may have the condition, or are navigating fertility treatment with a known diagnosis, this article aims to give you the knowledge to advocate for yourself and work effectively with your healthcare team.

What Is Endometriosis? The Basics Explained

Endometriosis is a chronic inflammatory disease characterised by the presence of endometrial-like tissue — tissue that resembles the lining of the uterus (the endometrium) — growing outside the uterine cavity. This tissue can implant on the ovaries, fallopian tubes, the outer surface of the uterus, the bowel, bladder, peritoneum (the lining of the abdominal cavity), and, in rare cases, even more distant sites.

Like the uterine lining, endometriotic implants respond to the hormonal fluctuations of the menstrual cycle — growing during the follicular phase and shedding during menstruation. But unlike the endometrium, which sheds through the cervix during a period, this misplaced tissue has no route of escape. The result is localised inflammation, the formation of scar tissue (adhesions), and, on the ovaries, the development of endometriomas — cysts filled with old menstrual blood ("chocolate cysts").

The exact cause of endometriosis remains debated. The most widely accepted theory is "retrograde menstruation" — menstrual blood flowing backwards through the fallopian tubes into the pelvic cavity — but this doesn't fully explain the condition, since retrograde menstruation is common but not all women develop endometriosis. Current evidence points to a complex interplay of genetic susceptibility, immune dysfunction, hormonal factors, and environmental influences.

How Endometriosis Affects Fertility

Endometriosis is associated with reduced fertility, though the relationship is complex and varies considerably with disease severity, location, and individual factors. Approximately 30–50% of women with endometriosis experience difficulty conceiving, and endometriosis is found in 20–50% of women investigated for infertility.

The mechanisms by which endometriosis impairs fertility are multiple and interconnected:

Distorted Pelvic Anatomy

In moderate to severe endometriosis (Stage III–IV on the ASRM classification), adhesions can distort or block the fallopian tubes, making it physically impossible for the egg to travel from the ovary to the uterus. Adhesions can also trap the ovaries against the uterus or bowel, interfering with follicle release and pick-up by the fimbria (the finger-like projections at the end of the fallopian tube).

Endometriomas and Ovarian Reserve

Endometriomas on the ovaries are of particular concern for fertility. The inflammatory environment within and around these cysts is toxic to the adjacent ovarian follicles, and the surgical removal of endometriomas carries its own risk of inadvertently removing healthy ovarian tissue. Studies consistently show that women with endometriomas have lower ovarian reserve (as measured by anti-Müllerian hormone, or AMH) than age-matched controls, and that ovarian reserve can decline further with each surgical intervention.

The Inflammatory Environment

Even in early-stage endometriosis without significant anatomical distortion, the chronic inflammatory environment created by active endometriotic implants can impair fertility through multiple mechanisms:

• Elevated levels of inflammatory cytokines (particularly IL-6, TNF-α, and prostaglandins) in peritoneal fluid and follicular fluid may be toxic to eggs and embryos
• Natural killer (NK) cells in the peritoneal fluid are abnormally elevated and may attack sperm and embryos
• The uterine receptivity (the "window of implantation") may be altered, making the endometrium less welcoming to embryo implantation
• Oxidative stress is elevated, which can damage egg DNA and reduce egg quality

Altered Tubal Function

Even when the fallopian tubes appear anatomically intact, endometriosis may impair their function. The cilia (hair-like structures that move the egg towards the uterus) can be damaged by the inflammatory environment, reducing the efficiency of egg transport.

Diagnosis: The Challenge of Getting Answers

Diagnosing endometriosis remains one of the most challenging aspects of the condition. The "gold standard" diagnosis requires laparoscopy — a surgical procedure under general anaesthesia — with histological (tissue) confirmation. Non-invasive diagnostic tools are improving but are not yet reliable enough to definitively diagnose or exclude the condition.

Key diagnostic approaches include:

Ultrasound

A transvaginal ultrasound performed by an experienced sonographer can detect endometriomas on the ovaries and, in expert hands, can identify signs of deep infiltrating endometriosis affecting the bowel or bladder. However, standard ultrasound cannot visualise superficial peritoneal endometriosis, and a normal ultrasound does not exclude the diagnosis.

MRI

MRI is superior to ultrasound for characterising complex or deep endometriosis and is valuable for surgical planning in advanced cases. It is not, however, routinely used for initial diagnosis.

Blood Tests

CA-125 is a blood marker that is elevated in some women with endometriosis, particularly those with more extensive disease. It is neither sensitive nor specific enough to be a reliable diagnostic test, but very elevated levels combined with other symptoms may prompt earlier surgical investigation.

Laparoscopy

Diagnostic laparoscopy allows direct visualisation of the pelvis and peritoneal cavity, enabling the surgeon to see, biopsy, and — if appropriately skilled and resourced — treat endometriotic lesions at the same time. In Europe, endometriosis centres of excellence increasingly advocate for excision surgery (complete removal of lesions) over ablation (burning/destroying lesions) for better long-term outcomes.

Treatment Options for Endometriosis-Related Infertility

The management of endometriosis-related infertility requires careful individualisation based on the severity of the condition, the woman's age, ovarian reserve, partner fertility, and personal preferences. European guidelines (ESHRE) provide a framework, but treatment pathways vary significantly between countries.

Surgery for Endometriosis

Surgical removal of endometriotic lesions, adhesions, and endometriomas can improve natural fertility in certain situations:

• For Stage I/II endometriosis, a large meta-analysis (the Canadian Collaborative Trial) found that laparoscopic removal of minimal to mild endometriosis significantly improved pregnancy rates compared to diagnostic laparoscopy alone
• For Stage III/IV endometriosis with tubal blockage or severe adhesions, surgery can restore normal anatomy and allow natural conception in some cases
• For endometriomas, the decision to operate is complex — surgery improves access to follicles during IVF but may reduce ovarian reserve; current ESHRE guidelines recommend against operating solely to improve IVF outcomes, unless the cyst is symptomatic or growing

Assisted Reproduction

IVF is increasingly the first-line treatment recommendation for women with more advanced endometriosis, older age, or reduced ovarian reserve. While endometriosis is associated with somewhat lower IVF success rates compared to other diagnoses, many women with endometriosis achieve successful pregnancies through IVF:

• Controlled ovarian stimulation protocols may need modification for women with reduced ovarian reserve
• Pre-treatment with GnRH analogues (typically 3–6 months) before IVF has been shown to improve implantation rates in some studies, though this remains an area of debate
• The use of preimplantation genetic testing (PGT-A) to select euploid (chromosomally normal) embryos may improve live birth rates in older women with endometriosis
• Frozen embryo transfer (FET) in a modified cycle may optimise the endometrial environment for implantation

IUI (Intrauterine Insemination)

IUI with ovarian stimulation may be appropriate for women with Stage I/II endometriosis, patent tubes, and adequate ovarian reserve, particularly as a less invasive step before IVF. Its success rates in endometriosis are lower than in unexplained infertility, and most European guidelines recommend progressing to IVF if IUI is unsuccessful after 3–4 cycles.

Lifestyle and Complementary Approaches

While lifestyle changes cannot cure endometriosis, there is growing evidence that certain approaches may reduce symptoms and support overall reproductive health:

Anti-inflammatory Diet

A diet rich in omega-3 fatty acids (oily fish, flaxseed, walnuts), antioxidants (colourful fruits and vegetables), and fibre, while reducing red meat, trans fats, and refined carbohydrates, is associated with lower endometriosis risk and reduced symptom severity in epidemiological studies. While not a treatment, dietary optimisation supports general health and may reduce inflammatory load.

Nutritional Supplements

Several supplements have been studied in endometriosis:

• N-acetyl cysteine (NAC): A small Italian trial found NAC superior to placebo for reducing endometrioma size; further research is needed
• Vitamin D: Deficiency is common in endometriosis; adequate levels may support immune regulation
• Omega-3 fatty acids: Reduce prostaglandins and inflammatory cytokines; several studies show reduction in endometriosis-related pain
• Magnesium: May reduce uterine cramping and pain; many women with endometriosis are deficient

Frequently Asked Questions

Can I get pregnant naturally with endometriosis?

Yes — many women with endometriosis conceive naturally. The likelihood of natural conception depends significantly on the stage and location of the disease, your age, and your ovarian reserve. Women with Stage I/II endometriosis (mild to moderate) who are under 35 with good ovarian reserve have reasonable chances of natural conception. Surgical treatment of endometriosis, particularly in Stage I/II disease, can improve natural fertility. For women with more advanced disease, older age, or reduced ovarian reserve, assisted reproduction may be recommended more promptly.

How does endometriosis affect egg quality?

Endometriosis is associated with reduced egg quality through several mechanisms: the inflammatory peritoneal environment creates oxidative stress that can damage egg DNA; endometriomas on the ovaries directly damage adjacent follicles; and elevated levels of certain inflammatory markers in follicular fluid may impair oocyte maturation. The good news is that antioxidant supplementation (CoQ10, vitamin E, C) may partially mitigate oxidative damage to eggs, and IVF with careful stimulation protocols can retrieve viable eggs from the majority of women with endometriosis.

Should I have surgery before trying IVF?

This is one of the most debated questions in reproductive endocrinology. Current ESHRE guidelines recommend that ovarian endometriomas should not be operated on solely to improve IVF outcomes, as surgery reduces ovarian reserve without consistently improving IVF success rates. However, if the endometrioma is symptomatic, growing, or very large (>4cm), surgery may be indicated. For deep infiltrating endometriosis, surgical excision at a specialist centre before IVF may improve implantation rates. This decision should be individualised with an experienced reproductive specialist.

Does endometriosis always get worse without treatment?

No. Endometriosis has a variable natural course. Some women have stable disease for many years without treatment, while others experience progression. Studies show that in about one-third of untreated women, the disease regresses; in another third, it remains stable; and in the remaining third, it progresses. Hormonal treatment (GnRH analogues, the pill, progestins) suppresses disease activity and prevents progression while on treatment, but disease typically recurs after stopping these medications.

I have endometriosis and have been told my ovarian reserve is low. What are my options?

Low ovarian reserve (typically reflected in low AMH and low antral follicle count) is common in women with endometriosis, particularly those who have had previous ovarian surgery. Options include: IVF with personalised stimulation protocols designed for low responders; consideration of egg banking (freezing eggs in advance of treatment) if fertility is not immediately desired; using donor eggs (from an anonymous or known donor) if own eggs are insufficient for IVF; or, in some cases, exploring embryo adoption. If your AMH is low and you're planning a family, it's important to discuss timing urgently with a reproductive specialist, as ovarian reserve can decline further over time.

Can endometriosis cause miscarriage?

The relationship between endometriosis and miscarriage risk is an area of ongoing research. Some studies suggest a slightly higher miscarriage risk in women with endometriosis, possibly related to altered uterine receptivity, immune dysregulation, and embryo quality issues. However, the evidence is not consistent across all studies. Women with endometriosis who have repeated miscarriages should be investigated for all standard recurrent miscarriage causes as well as endometriosis-specific factors.

What is the difference between endometriosis and adenomyosis, and does adenomyosis affect fertility too?

Endometriosis involves endometrial-like tissue outside the uterus; adenomyosis involves endometrial tissue growing into the muscular wall of the uterus (the myometrium). The two conditions frequently coexist. Adenomyosis is increasingly recognised as a cause of reduced implantation rates and recurrent miscarriage. It can be identified on transvaginal ultrasound or MRI. Treatment options for fertility-affecting adenomyosis are limited; some evidence suggests surgical excision of focal adenomyosis can improve IVF outcomes, and GnRH analogue pre-treatment may improve the uterine environment before embryo transfer.

Are there endometriosis centres of excellence in Europe that I should seek out?

Yes. The European Endometriosis League (EEL) and ESHRE advocate for care at specialist endometriosis centres, particularly for complex disease. These centres combine expertise in excision surgery, reproductive medicine, gastroenterology (for bowel endometriosis), and urology (for urinary tract involvement). Germany, Belgium, France, Italy, and the Netherlands have particularly well-developed networks of endometriosis specialists. Seeking care at a specialist centre rather than a general gynaecology service can make a significant difference for women with moderate-to-severe endometriosis.

Will pregnancy cure my endometriosis?

Pregnancy does not cure endometriosis. While the hormonal environment of pregnancy (particularly the sustained high progesterone levels) often leads to temporary suppression of endometriotic lesion activity, and some women report improvement in symptoms during and after pregnancy, endometriosis typically returns after delivery and the resumption of menstruation. The "get pregnant to cure endometriosis" advice that some women still receive is outdated and unhelpful.

What support resources are available for endometriosis patients in Europe?

Several excellent resources exist for European patients. The European Endometriosis Alliance and national patient organisations (such as Endometriosis UK in Britain, Endometriose Vereinigung Deutschland in Germany, and EndoFrance in France) provide information, support groups, and advocacy. The ESHRE patient guide on endometriosis, available for free on the ESHRE website, is an excellent evidence-based resource. Online communities can also provide valuable peer support, though they should not replace medical advice.