Objective: The purpose of this study was to assess the use-effectiveness of oral contraceptives (OCs) in Europe according to body mass index (BMI), weight, age, and other factors.
Study design: In a planned secondary analysis, we used data from the European Active Surveillance Study on Oral Contraceptives, which was a prospective active cohort surveillance study of 59,510 OC users, to assess the effectiveness of OCs overall and by BMI, weight, age, duration of use, ethinylestradiol dose, regimen type, starting/switching status, and parity. Self-reported unplanned pregnancies during OC use were confirmed by interview.
Results: An analysis of OC effectiveness (112,659 women-years of exposure and 545 unplanned pregnancies) found little variation in effectiveness by BMI/weight. Failure rates decreased after 30 years of age and with an increasing duration of use.
Conclusion: OC users in Europe reported high contraceptive effectiveness with "typical use." Failure rates decreased with age and duration of use. BMI and weight had little, if any, influence on effectiveness.