When used under routine conditions, vaginal ring (VR) and combined oral contraceptives (COC) have similar venous thrombolism (VTE) risks, according to a prospective, controlled, non-interventional cohort study.
The “Transantlatntic Active Surveillance on Cardiovascular Safety of NuvaRing” (TASC) included 33,704 subjects from the United States and five European countries, and investigated the risks of short and long-term use of VR and COCs in a population representative of routine use.
One cohort used a VR containing etonogestrel and ethinylestradiol. A second cohort used COCs. All subjects were new users—starters, switchers or restarters—and were recruited by 1,661 study centers with a two- to four-year follow-up. Self-reported outcomes were verified by health care professionals. Analysis adjustments were made using the Cox regression model.
Results, presented by Juergen Dinger, MD, PhD, of the Berlin Center for Epidemiology at the American Congress of Obstetricians and Gynecologists’ Annual Clinical Meeting, are based on 46,806 woman-years (WY) of follow-up. Comprehensive measures were taken to ensure a low follow-up loss. Overall, 34 confirmed VTEs occurred in current users of VR or COCs.
The overall VTE incidence for users of hormonal contraceptives is 9.4/10,000 WY, respectively (95% confidence interval [CI], 6.5-13.1). For VR and COCs, the VTE incidence is 8.8 and 9.9/10,000 WY, respectively.
The crude hazard ratio for VR vs. COCs is 0.9 (95% CI: 6.5-13.1). After making allowances for age, body mass index, duration of current VR/COC use and family history of VTE, the adjusted HR is 0.8 (95% CI: 0.4-1.6).
Results indicate a similar risk of VTE for users of VR or COC under conditions of routine use.