LAUSR

470,000 women years of exposure. The observed prevalence of prognostic factors at baseline showed typical features of US and European COC users. However, the mean age in the E2/E2Val cohort was higher compared to the EE%30mg cohort (31.7 years 9.76 and 26.1 years 7.89, respectively). A time-to-event analysis of the VTE data was carried out based on the extended Cox model. Validity of the model was demonstrated by the standardized differences summarized over strata as weighted average yielded upon PS subclassification, which were consistently <0.25 and mostly <0.1. A comparison between cohorts showed a decreased risk of venous thromboembolism in users of COCs containing E2/E2Val vs users of COCs containing EE%30mg; adjusted hazard ratio: 0.49 (95% CI, 0.28-0.84). A risk reduction in the E2/ E2Val cohort was also observed with regards to arterial thromboembolic events; adjusted hazard ratio: 0.26 (95% CI, 0.08-0.83). CONCLUSIONS: Data presents a solid safety assessment of combined hormonal preparations in over 200,000 pre-menopausal women and shows a decreased cardiovascular risk of E2/E2Val when compared to low-dose EE. This provides reassurance for current users of E2/E2Val-containing COCs and opens new perspectives for the development of safe and effective endometriosis treatments, such as the recently developed product containing E2/NETA, in combination with relugolix. SUPPORT: This analysis was supported by a grant from Myovant Sciences. Dataset is owned by ZEG Berlin GmbH.