L26/P-332 Time to live birth and cumulative live birth rates in women with and without endometriosis undergoing in vitro fertilization: analysis of over 6,000 patients

Abstract Study question Is the time to live birth and the cumulative live birth rate different in women with endometriosis vs no endometriosis after one in vitro fertilization(IVF)cycle? Summary answer Endometriosis did not modify the time to live birth (TTLB) and the cumulative live birth rate (CLBR) in women undergoing their first IVF cycle. What is known already Endometriosis is a common cause of infertility and has been associated with impaired oocyte quality and reduced ovarian response. The number of oocytes retrieved is a key predictor of CLBR, a clinically meaningful outcome of IVF success. However, evidence on the impact of endometriosis on CLBR remains conflicting, with heterogeneous results. It is hypothesised that TTLB may be longer in women with endometriosis due to lower ovarian reserve, the need for repeated cycles, or potential need for additional interventions. To date, no previous studies have specifically compared TTLB between women with and without endometriosis, creating uncertainty in counselling and prognosis. Study design, size, duration This retrospective single-center cohort study included 6,353 women undergoing their first IVF/Intracytoplasmic Sperm Injection (ICSI) cycle at our University Hospital between January 2017 and December 2024. Women were stratified according to primary infertility diagnosis into endometriosis (n = 744) and non-endometriosis (n = 5,609) groups. Endometriosis was diagnosed by transvaginal ultrasound according to the International Deep Endometriosis Analysis (IDEA) criteria. Participants were followed from a single oocyte retrieval until live birth or utilization of all embryos. Participants/materials, setting, methods Eligible participants were infertile women aged 18–43 years undergoing their first IVF/ICSI cycle at our center. The primary aim of the study was to evaluate TTLB and CLBR according to the number of oocytes retrieved, stratified by endometriosis diagnosis. A multivariable logistic regression model assessed the CLBR, adjusted for female age and oocyte yield, in women with or without endometriosis. Main results and the role of chance Overall, 6353 women were included, with 744 (11.7%) diagnosed with endometriosis. Women with endometriosis were younger (36.3±3.8 vs 37.4±3.9 years, p < 0.001) and exhibited lower ovarian reserve parameters: Anti-Müllerian Hormone (1.8±1.8 vs 2.1±2.1 ng/mL, p < 0.001) and Antral Follicle Count (11.0±7.3 vs 12.8±8.0, p < 0.001). Regarding ovarian stimulation outcomes, the endometriosis group showed fewer oocytes retrieved (9.7±7.1 vs 10.7±7.4, p < 0.001) and mature (MII) oocytes (7.4±5.6 vs 8.1±5.8, p = 0.001), with no significant differences in fertilization (5.74±4.94 vs 5.95±4.81, p = 0.132) or in the number of blastocysts (2.85±3.26 vs 2.82±2.98, p = 0.383). CLBR did not differ between women with and without endometriosis (39.9% vs 37.6%, p = 0.213). Multivariable analysis confirmed that, at the same female age and oocyte yield, endometriosis was not independently associated with CLBR (aOR 1.03, 95% CI 0.87–1.22). Time-to-event analysis showed no significant difference in TTLB between groups in unadjusted analysis (log-rank p = 0.233). At 48 months, cumulative live birth was 41.2% in women with endometriosis and 38.5% in those without. TTLB probabilities at 12, 24, 36 and 48 months were otherwise comparable between groups, indicating similar chances of achieving live birth over time. These findings suggest that observed similarities are unlikely due to chance. Limitations, reasons for caution The main limitation of this study is its retrospective design. Despite the sample size and the use of multivariable regression models to account for confounding factors, the presence of residual bias cannot be excluded. Furthermore, endometriosis severity and phenotype were not systematically classified. Wider implications of the findings The current study demonstrates that, despite reduced ovarian reserve, endometriosis did not negatively affect CLBR or TTLB. When similar oocyte yield was achieved, its prognostic value remained comparable between groups. These findings have important counselling implications, supporting similar expectations and treatment strategies in women with and without endometriosis. Trial registration number No