Impact of estrogen type on cardiovascular safety of combined oral contraceptives.

OBJECTIVES: The International Active Surveillance study "Safety of Contraceptives: Role of Estrogens" (INAS-SCORE) investigated the cardiovascular risks associated with the use of a combined oral contraceptive (COC) containing dienogest and estradiol valerate (DNG/EV) compared to established COCs in a routine clinical setting.

STUDY DESIGN: Transatlantic, prospective, noninterventional cohort study conducted in the United States and seven European countries with two main exposure groups and one exposure subgroup: new users of DNG/EV and other COC (oCOC), particularly levonorgestrel-containing COCs (LNG). All self-reported clinical outcomes of interest (OoI) were validated via attending physicians and relevant source documents. Main OoI were serious cardiovascular events (SCE), particularly venous thromboembolic (VTEs) events. Comprehensive follow-up procedures were implemented. Statistical analyses were based on Cox regression models.

RESULTS: A total of 50,203 new COC users were followed up for up to 5.5years (mean value, 2.1years). Overall 20.3% and 79.7% of these women used DNG/EV and oCOC (including 11.5% LNG users), respectively. A low loss to follow-up of 3.1% was achieved. Based on 47 (VTE) and 233 (SCE) events, the primary analysis (European data set) yielded adjusted hazard ratios for DNG/EV vs. oCOC of 0.4 and 0.5, respectively. The upper bounds of the 95% confidence intervals were 0.98 (VTE) and 0.96 (SCE). The corresponding hazard ratios for DNG/EV vs. LNG showed similar point estimates but the confidence intervals included unity.

CONCLUSION: DNG/EV is associated with similar or even lower cardiovascular risk compared to oCOC and LNG.

IMPLICATION STATEMENT: A COC containing DNG and EV is associated with similar or even lower cardiovascular risk compared to COCs containing levonorgestrel or other progestogens.