Contraceptive vaginal ring effectiveness is maintained during 6 weeks of use: a prospective study of normal BMI and obese women.

BACKGROUND: A single study shows that contraceptive vaginal ring (CVR) use for up to 35 days in women with a normal body mass index (BMI) maintains serum hormone levels sufficient to suppress ovulation. This study is intended to confirm those results and to evaluate prolonged CVR use up to 42 days in both normal BMI and obese women. STUDY
DESIGN: Twenty women with a normal BMI and 20 obese women enrolled in a prospective open label clinical study of ethinyl estradiol (EE) and etonogestrel (ENG) pharmacokinetics during six weeks of use of a single CVR. Participants underwent twice-weekly evaluations to determine serum hormone concentrations, ovarian follicle development, endometrial thickness and bleeding patterns.
RESULTS: Thirty-seven women completed follow-up including eighteen women with a normal BMI and nineteen obese women. EE and ENG concentrations remained in therapeutic range for all women. Follicular development and endometrial proliferation were minimal. By the sixth week, 30% of participants reported spotting or bleeding.
CONCLUSIONS: A single CVR used for 6 weeks demonstrates therapeutic serum levels of EE and ENG among women with normal and obese BMI. Women who forget to remove the CVR at day 21 may well have continued contraceptive protection during the next 3 weeks.