L26/O-140 Endometriosis and ovarian reserve: a cohort study

Abstract Study question Is endometriosis associated with reduced ovarian reserve, as measured by Anti-Müllerian hormone (AMH) levels, independent of surgical intervention? Summary answer Endometriosis was associated with lower AMH levels, suggesting reduced ovarian reserve, independent of surgical intervention. What is known already Endometriosis is a chronic gynecological condition characterized by ectopic endometrial-like tissue, affecting approximately 10% of reproductive-aged women worldwide. Endometriosis may impair ovarian stroma through inflammatory or fibrotic mechanisms, or iatrogenically through surgical intervention. Whether endometriosis itself, independent of surgery, adversely affects ovarian tissue remains unclear. Prior studies evaluating the association between endometriosis and AMH levels, a robust, cycle-independent biomarker of ovarian reserve, have been limited by small sample sizes and limited generalizability. We therefore examined the association between endometriosis and ovarian reserve using AMH levels, comparing women with medically versus surgically managed endometriosis within a universal healthcare system. Study design, size, duration Using linked administrative healthcare data, we conducted a retrospective cohort study of 58,177 women aged 18–50 years who underwent AMH testing in Ontario, Canada between 2013 and 2024. At least five years of prior residency were required to ascertain endometriosis diagnosis and management. Participants/materials, setting, methods Exposure was endometriosis (yes/no), identified using a validated algorithm based on ≥ 2 outpatient physician billings (ICD-9 617) or a hospital admission, same-day surgery, or emergency department visit (ICD-9 617 or ICD-10 N80). Endometriosis was classified as medically or surgically managed. The outcome was AMH level (ng/mL). Standardized differences assessed baseline differences. Differences in median AMH levels were estimated using quantile regression adjusted for relevant covariates. Main results and the role of chance The cohort included 54,808 women without endometriosis (94.2%) and 3369 with endometriosis (5.8%). Among those with endometriosis, 2119 (62.9%) were medically managed and 1250 (37.1%) underwent surgical management. Mean age (SD) was similar in women without vs with endometriosis (34.8 [5.5] vs 34.6 [4.9] years). Women with endometriosis were more likely to have additional gynecologic conditions, including uterine fibroids, abnormal uterine bleeding, and infertility. Median (IQR) AMH levels were lower in women with endometriosis than in those without (1.67 ng/mL [0.74–3.13] vs 2.03 ng/mL [0.89–3.76]). After adjustment, endometriosis was associated with lower median AMH levels (1.63 ng/mL, 95% CI 1.52–1.74) compared with women without endometriosis (1.96 ng/mL, 95% CI 1.87–2.06; p < 0.001). Adjusted median AMH levels were similar between surgically and medically managed endometriosis (1.62 ng/mL, 95% CI 1.49–1.74 vs 1.65 ng/mL, 95% CI 1.52–1.77; p = 0.68). Limitations, reasons for caution AMH testing is typically performed during infertility evaluations; accordingly, 86.8% of women had a diagnosis of infertility, which may limit generalizability to women without fertility concerns. Administrative data studies may result in misclassification of exposure, residual confounding, and inability to assess disease severity. Wider implications of the findings These findings suggest that endometriosis itself, including among individuals not undergoing surgical management, may be associated with reduced ovarian reserve. This information may inform counselling and decision-making regarding fertility assessment and treatment planning in women with endometriosis. Trial registration number No