L26/P-336 Impact of advanced endometriosis on in vitro fertilization outcomes: a matched case–control study of 558 first IVF cycles

Abstract Study question Does advanced-stage endometriosis adversely affect IVF outcomes when patients are matched for key confounding variables as age, ovarian reserve and dose of gonadotropins? Summary answer Advanced-stage endometriosis does not appear to significantly impair clinical pregnancy or cumulative live birth rates in IVF when key prognostic factors are adjusted What is known already Endometriosis is a common cause of infertility and has traditionally been associated with poorer IVF outcomes, particularly in advanced stages. Proposed mechanisms include reduced ovarian reserve, altered folliculogenesis, pelvic inflammation, oxidative stress and impaired endometrial receptivity. Two earlier meta-analyses suggested lower implantation, clinical pregnancy and live birth rates in women with severe endometriosis. However, two recent systematic reviews and two case-control studies have failed to find significant differences between endometriosis patients and controls, highlighting the role of confounding factors such as age, ovarian reserve, prior surgery and male factor infertility, which may explain the previously reported detrimental effects. Study design, size, duration A retrospective matched case–control study including 558 women undergoing their first IVF cycle between January 2009 and December 2023 at a tertiary academic reproductive medicine centre was conducted. A total of 279 women with advanced endometriosis (stage III–IV) were matched 1:1 with controls without endometriosis considering the following confounding variables: age, ovarian reserve (AMH and AFC), male factor infertility, gonadotropin dose and study period. Participants/materials, setting, methods The cases were women with ultrasound- or surgically diagnosed advanced endometriosis. The patients in the control group were matched 1:1 for age, ovarian reserve (AMH and AFC), male factor, gonadotropin dose and study period. IVF outcomes were compared using univariate and multivariate logistic regression analyses adjusting for main confounders: age, AMH, gonadotropin dose and sperm count. Primary outcome was cumulative live birth rate; secondary outcomes included clinical pregnancy and miscarriage rates. Main results and the role of chance Baseline characteristics were comparable between groups, reflecting the matching strategy. Women with advanced endometriosis showed a slightly lower antral follicle count, while AMH levels were similar. Ovarian stimulation parameters, total and mature oocytes retrieved, embryo yield and the proportion of good-quality embryos did not differ meaningfully between groups. Cumulative clinical pregnancy rates were identical in women with advanced endometriosis and controls (48.0% in both groups). Similarly, cumulative live birth rates were comparable (43.9% vs 43.4%). Among women achieving pregnancy, miscarriage rates did not differ substantially between groups (37.2% vs 30.8%). In the unadjusted analysis, advanced endometriosis was not associated with cumulative live birth (OR 1.02; 95% CI 0.73–1.43). This finding remained unchanged after adjustment for age, ovarian reserve and gonadotropin dose (adjusted OR 1.05; 95% CI 0.27–4.02). These findings suggest that advanced endometriosis is not independently associated with poorer IVF outcomes, and that any observed differences are likely attributable to chance rather than to the condition itself. Limitations, reasons for caution Main limitations of our study include the retrospective nature of the data, the lack of histological confirmation in most cases, the potential risk of residual confounding despite careful matching, the absence of data on adenomyosis and endometrial receptivity, and the single-centre setting, which may limit generalisability. Wider implications of the findings When appropriately matched, IVF success rates in women with advanced endometriosis appear comparable to those of controls. These findings suggest that individualized treatment approaches should be considered, taking into account factors such as age, ovarian reserve parameters and appropriate gonadotropin dosing. Trial registration number No