Endometriosis affects roughly one in ten women of reproductive age worldwide, a figure cited so often it has become the default shorthand for the disease’s reach. But that “about 10%” estimate conceals enormous variation depending on who is being studied and how the diagnosis is made. The true prevalence remains genuinely uncertain, because endometriosis can only be definitively confirmed through surgery, and many people with the condition go years without a diagnosis. What we do know is that the numbers shift dramatically across different populations, and the gap between what insurance claims data suggest and what clinical studies find is wide enough to affect how the disease gets funded and treated.
Why the Numbers Are So Hard to Pin Down
Unlike conditions that show up on a blood test or a standard imaging scan, endometriosis has historically required laparoscopy with tissue biopsy for a definitive diagnosis. That means the only way to get a precise prevalence count is to surgically examine a representative sample of the population, something no study has done or could ethically do. Every prevalence estimate is therefore an indirect measurement shaped by the population sampled and the diagnostic standard applied.
A narrative review in the International Journal of Gynecology & Obstetrics illustrates the problem starkly. Health insurance claims data suggest roughly 1% of women are affected. Clinical studies using surgical confirmation put the figure closer to 7%. Studies focused on women who already have symptoms push it to about 21%.1International Journal of Gynecology & Obstetrics. Assessing the true prevalence of endometriosis: A narrative review of literature data Those aren’t conflicting answers to the same question; they’re answers to different questions, each shaped by who walked through the clinic door and what tools were used to look.
Self-reported diagnosis adds another layer of uncertainty. When researchers compared women’s self-reports of endometriosis against their medical records across four cohorts, confirmation rates ranged from 32% to 89%, depending on how “confirmed” was defined and which records were checked. In one Swedish twin study, 82% of self-reports were confirmed when researchers reviewed full medical records, but only 32% were confirmed when checked against inpatient hospital registry data alone.2Human Reproduction. Validity of self-reported endometriosis: a comparison across four cohorts The choice of what counts as a “gold standard” for diagnosis can swing prevalence estimates by a factor of two or more.
Diagnostic delays compound the problem. Getting a diagnosis of endometriosis still takes years on average in many health systems, meaning a meaningful portion of people living with the disease at any given time are not yet captured in any dataset.3Journal of Endometriosis and Pelvic Pain Disorders. Navigating endometriosis diagnostic delay in 2040: Future directions in noninvasive diagnosis This creates a circular problem: the disease appears less common than it is because the diagnostic pathway is slow, and the diagnostic pathway receives less urgency because the disease appears less common than it is.
Prevalence in Clinical Populations
The clearest prevalence data come from studies of women undergoing surgery for a specific reason, since the surgeon can directly visualize and biopsy endometrial-like tissue outside the uterus. These numbers are consistently higher than general population estimates, but they vary depending on the reason for surgery.
Among women investigated for infertility, endometriosis shows up in a large fraction of cases. One review estimated the probability of endometriosis in people with infertility at up to about 50%.4Best Practice & Research Clinical Obstetrics & Gynaecology. Epidemiology of infertility in women with endometriosis A systematic review pooling multiple studies put the figure at about 31%, though with wide confidence intervals.5PubMed Central. A systematic review on the prevalence of endometriosis in women The range reflects differences in how infertility was defined and which surgical populations were studied, but the direction is consistent: endometriosis is far more common among people struggling to conceive than in the general population.
For chronic pelvic pain, a commonly cited estimate is about 28% to 33%, based on compilations of studies in which women with persistent pain underwent laparoscopy. But that headline number masks wild variation. The individual studies behind it reported prevalence anywhere from 2% to 74%.6Gynecologic and Obstetric Investigation. The Prevalence of Endometriosis in Women with Chronic Pelvic Pain In one study of women referred for chronic pelvic pain who underwent laparoscopy, biopsy-proven endometriosis was found in 28%.7PubMed. The prevalence of interstitial cystitis, endometriosis, adhesions, and vulvar pain in women with chronic pelvic pain That same systematic review found chronic pelvic pain populations had an overall pooled prevalence of about 42%.8PubMed Central. A systematic review on the prevalence of endometriosis in women
Even among women with no pelvic symptoms at all, endometriosis is not rare. A prospective study of 360 asymptomatic women undergoing laparoscopic tubal sterilization found endometriosis in 10%.9PubMed. Clinical presentation of endometriosis identified at interval laparoscopic tubal sterilization: Prospective series of 465 cases A systematic review pooling asymptomatic populations estimated the prevalence at about 23%.10PubMed Central. A systematic review on the prevalence of endometriosis in women The gap between 10% in one study and 23% in the pooled analysis likely reflects differences in what counted as “asymptomatic” and how carefully the surgeon looked. Regardless, the finding that a substantial fraction of people with no pain still have the disease complicates any simple link between symptoms and prevalence.
Women undergoing surgery for other benign gynecological conditions, like fibroids or ovarian cysts unrelated to endometriosis, show a pooled prevalence of about 34%.11Journal of Endometriosis and Pelvic Pain Disorders. The frequency of endometriosis in the general and selected populations: A systematic review This group is interesting because it represents people who are surgically accessible but not specifically suspected of having endometriosis, offering a kind of incidental detection rate.
The Global Burden and How It Is Changing
A comprehensive analysis using data from the Global Burden of Disease study tracked endometriosis from 1990 to 2021. By 2021, an estimated 22.3 million women worldwide were living with the condition, up from about 19.9 million in 1990. But the age-standardized prevalence rate actually declined over that period, dropping from roughly 374 per 100,000 in 1990 to about 276 per 100,000 in 2021.12PubMed Central. Global burden of endometriosis from 1990 to 2021 and projections to 2050: a comprehensive analysis based on the global burden of disease study 2021 The total number of cases rose because the global female population grew, but the rate per person edged downward. Whether that decline reflects genuine biological change, shifts in diagnostic patterns, or methodological artifacts of the modeling is an open question.
The same analysis found that prevalence peaked in the 25 to 29 age range, with a rate nearly three times the overall age-standardized figure, and remained relatively stable across the broader 20 to 49 age window.13PubMed Central. Global burden of endometriosis from 1990 to 2021 and projections to 2050: a comprehensive analysis based on the global burden of disease study 2021 This peak in the late twenties aligns with the biology: endometriosis is an estrogen-dependent disease, and this is the period when hormonal activity and diagnostic opportunity overlap most.
Endometriosis at the Extremes of Reproductive Age
Although endometriosis is most commonly diagnosed in the twenties and thirties, it exists at both ends of the reproductive spectrum. In adolescents, the disease often looks different. A prospective cohort study comparing adolescents and adults with endometriosis found that painful periods were more frequent in younger patients, lasted longer, and came with higher pain scores.14PubMed Central. Endometriosis in Adolescents: A Closer Look at the Pain Characteristics and Symptoms: A Prospective Cohort Study Younger patients also tend to have different patterns of disease: a study of over 1,300 women with surgically confirmed endometriosis found that women 24 and under had significantly more isolated superficial lesions and less deep infiltrating disease compared to older patients.15Human Reproduction. Distribution of endometriosis phenotypes according to patients’ age in adult women with surgical evaluation This may reflect earlier stages of disease or a different natural history in younger bodies.
After menopause, endometriosis becomes rare, but it does not vanish entirely. Literature on the topic remains sparse, and most of what has been published focuses on how common it is rather than on understanding its mechanism in a low-estrogen environment.16PubMed Central. Endometriosis in Menopause-Renewed Attention on a Controversial Disease What distinguishes postmenopausal endometriosis from the premenopausal form is its behavior. It tends to produce more fibrosis and adhesions rather than active bleeding lesions, shows a greater tendency to spread to organs outside the reproductive tract, and carries a higher risk of malignant transformation.17PubMed. Postmenopausal endometriosis: drawing a clearer clinical picture Imaging findings reflect this shift toward scarring and fibrotic tissue, with occasional cystic components.18RadioGraphics. Postmenopausal Endometriosis: Clinical Insights and Imaging Considerations When postmenopausal endometriosis is treated, surgery is generally preferred over hormonal therapy, since the hormonal environment that drives premenopausal disease is already absent.
Racial and Ethnic Disparities in Diagnosis
The question of whether endometriosis is more common in some racial or ethnic groups than others has been debated for over a century, but the available data suggest the disparities in diagnosis rates are at least partly driven by unequal access to care and diagnostic bias.19PubMed Central. Revisiting the impact of race/ethnicity in endometriosis
A systematic review and meta-analysis found that compared to White women, Black women were roughly half as likely to be diagnosed with endometriosis, while Asian women were about 60% more likely to receive a diagnosis.20BJOG: An International Journal of Obstetrics & Gynaecology. Influence of race/ethnicity on prevalence and presentation of endometriosis: a systematic review and meta‐analysis The difference for Hispanic women was not statistically significant in that analysis. Whether these patterns reflect true biological differences in disease frequency, differences in symptom presentation, or systematic differences in who gets evaluated and diagnosed remains contested. Historical assumptions that endometriosis was a “career woman’s disease” primarily affecting affluent White women likely delayed diagnosis in other populations for decades, and the research base is still catching up.
Family History and Genetic Risk
Endometriosis clusters in families, and the genetic contribution is substantial. A large twin study estimated that additive genetic factors account for about 47% of the variation in whether someone develops the disease, with the remaining 53% attributable to individual environmental factors.21PubMed. Heritability of endometriosis That is a strong genetic signal, comparable to conditions like asthma or type 2 diabetes.
Having a first-degree relative with endometriosis dramatically increases your chances. In one study, endometriosis was found in about 9.5% of first-degree relatives of women with the condition, compared to just 1% of controls, yielding roughly ten times the odds.22PubMed. Familial aggregation of endometriosis in the Yale Series An earlier Scandinavian study found a similar pattern: about 4% of mothers and 5% of sisters of affected women had the disease, compared to less than 1% in control families. Women with a positive family history also tended to have more severe disease.23PubMed. The familial risk of endometriosis Researchers have identified dozens of genetic loci associated with endometriosis risk through large genome-wide studies, but no single gene dominates. It is a classic polygenic condition where many small genetic effects combine with environmental exposures.
Conditions That Travel With Endometriosis
People with endometriosis are more likely to be diagnosed with a range of other conditions, and some of these overlaps are large enough to matter for clinical care. Autoimmune diseases are the most studied co-travelers. A large case-control study found that about 5% of endometriosis patients received at least one autoimmune diagnosis within two years, compared to about 1.4% in a matched comparison group.24npj Women’s Health. Endometriosis and autoimmunity: a large-scale case-control study of endometriosis and 10 distinct autoimmune diseases
A systematic review and meta-analysis found elevated risk for several specific autoimmune conditions in women with endometriosis:
- Lupus (SLE): roughly 35-75% higher odds compared to women without endometriosis
- Sjögren syndrome: about 76% greater odds
- Rheumatoid arthritis: about 50% greater odds
- Inflammatory bowel disease: about twice the odds
- Coeliac disease: about four times the odds, though based on limited data
These associations held across multiple study designs, though the review noted that many individual studies were small or had methodological limitations.25PubMed Central. The association between endometriosis and autoimmune diseases: a systematic review and meta-analysis The reasons for this clustering are not fully understood, but endometriosis involves chronic inflammation and immune system dysfunction that may share pathways with autoimmune conditions.
Irritable bowel syndrome is another frequent companion. A meta-analysis found that the pooled prevalence of IBS in women with endometriosis was about 23%, with individual studies reporting rates from 11% to 52%.26PubMed Central. Endometriosis and irritable bowel syndrome: A systematic review and meta-analyses One cross-sectional study found that nearly half of endometriosis patients had previously been diagnosed with IBS.27PubMed Central. Prevalence of irritable bowel syndrome in endometriosis patients: A cross-sectional study The symptom overlap between pelvic endometriosis and IBS (bloating, cramping, altered bowel habits) means some of these cases may represent misdiagnosis in one direction or the other, but it also appears that the two conditions genuinely coexist more often than chance would predict.
The Link to Ovarian Cancer
Endometriosis is associated with an increased risk of ovarian cancer, a connection that causes understandable anxiety. A large meta-analysis found an overall elevated risk with an odds ratio of about 1.8, meaning roughly 80% higher relative risk compared to women without endometriosis.28PubMed. Risk, Prevalence and Survival Outcomes of Ovarian Cancer in Women With Endometriosis: The Endocancer Systematic Review and Meta-Analysis A study published in JAMA found the strongest associations with clear cell carcinoma, where the risk was roughly 11 times higher in women with endometriosis, and for women who had deep infiltrating endometriosis or ovarian endometriomas specifically, the overall ovarian cancer risk was nearly tenfold higher than for women without the disease.29JAMA. Endometriosis Typology and Ovarian Cancer Risk
Those relative increases sound alarming, but the absolute risk remains low. The probability of malignant transformation of endometriosis in premenopausal women is estimated at around 1%.30PubMed Central. New insights about endometriosis-associated ovarian cancer: pathogenesis, risk factors, prediction and diagnosis and treatment Ovarian cancer itself is uncommon, so even a several-fold increase in relative risk translates to a small absolute increase for any individual woman. That said, the connection is significant enough that some researchers have proposed tailored screening or surveillance strategies for people with specific endometriosis subtypes, particularly those with ovarian endometriomas.
The Economic Weight of a Common Disease
Because endometriosis affects so many people and often goes years without treatment, its economic footprint is substantial. A review of the literature found that direct medical costs ranged from about $1,500 to over $20,000 per patient per year, with surgery as the main cost driver. Indirect costs from lost productivity ran between roughly $4,500 and $14,000 per patient per year.31PubMed. Economic Implications of Endometriosis: A Review An Australian national survey found that productivity losses actually dwarfed medical costs, with lost work time accounting for the bulk of the estimated $20,900 in total per-person annual costs. Scaled to the Australian population assuming 10% prevalence among reproductive-age women, the total annual burden was estimated at $6.5 billion.32PubMed Central. The cost of illness and economic burden of endometriosis and chronic pelvic pain in Australia: A national online survey
In the U.S., a study of patients with Medicaid insurance found that women with endometriosis incurred mean annual direct health care costs of about $13,700, compared to roughly $5,800 for matched controls without the condition.33PubMed Central. Health Care Utilization and Costs Associated with Endometriosis Among Women with Medicaid Insurance The gap reflects not just the cost of treating endometriosis itself, but the cascade of related health care needs, from pain management to fertility treatment to managing associated conditions. In every study that has looked at it, the economic burden falls heavily on the patients themselves, in both out-of-pocket expenses and career disruption, a pattern that connects back to the long diagnostic delays and the lack of a cure.
How Endometriosis Subtype Affects What We Count
Endometriosis is not a single uniform disease but comes in several forms: superficial peritoneal lesions, ovarian endometriomas (sometimes called “chocolate cysts”), and deep infiltrating endometriosis that invades into organs like the bowel or bladder. The distribution of these subtypes shifts with age. In women 24 and younger, isolated superficial lesions are relatively more common, appearing in about 32% versus 26% of older women. Deep infiltrating disease, meanwhile, is found less frequently in younger patients.34Human Reproduction. Distribution of endometriosis phenotypes according to patients’ age in adult women with surgical evaluation
This matters for prevalence estimates because some diagnostic methods are better at catching certain subtypes than others. Ultrasound and MRI can often detect ovarian endometriomas and deep infiltrating nodules but are poor at finding superficial lesions, which require direct visualization during surgery. If prevalence studies rely on imaging rather than surgical exploration, they will systematically undercount the most common form of the disease in younger patients. As noninvasive diagnostic tools improve, prevalence estimates are likely to shift again, not because the disease itself is changing, but because we are getting better at seeing what was always there.