Unintended pregnancy rates differ according to combined oral contraceptive – results from the INAS-SCORE study

Abstract

Objectives: To estimate the real-use contraceptive effectiveness of the combined oral contraceptive (COC) containing dienogest and oestradiol valerate (DNG/oEV) compared to other combined oral contraceptives (oCOC) and particularly, levonorgestrel-containing OCs (LNG).

Methods: Prospective, non-interventional cohort study with two main exposure groups and one exposure subgroup: new users of DNG/oEV and oCOC, with the subgroup, LNG. In a planned secondary analysis, pregnancy outcomes were investigated, including contraceptive failure. The influence of age, parity and OC-type were assessed.

Results: 30,098 COC users were followed for a total oral contraceptive exposure time of 68,362 woman-years (WY) and 287 unintended pregnancies were reported. The overall contraceptive failure rate in the European population was 0.4 events/100 WY (95% CI, 0.4–0.5). DNG/oEV showed lower contraceptive failure rates compared to the comparators. This difference was maintained when the study population was restricted to women aged 18–35 years; the pearl index (PI) for this demographic for DNG/oEV was 0.37 (95% CI 0.24–0.54) and 0.76 (95% CI 0.56–1.01) for LNG. The hazard ratios (HRs) adjusted for age, parity, smoking and BMI were 0.7 (95% CI, 0.5–0.98, p = .04) and 0.5 (95% CI, 0.3–0.8, p < .01) for DNG/oEV versus oCOC and LNG, respectively. The corresponding adjusted HRs in women aged 25 years or younger were 0.6 (95% CI 0.4–1.1) and 0.4 (95% CI, 0.2–0.8), respectively.

Conclusions/discussion: DNG/oEV showed improved contraceptive effectiveness compared with oCOC and particularly LNG-COC when adjusted for age, parity, user status and smoking.

摘要

目的：评估含地诺孕素和戊酸雌二醇 (DNG/oEV) 的复方口服避孕药 (COC) 与其他复方口服避孕药 (oCOC), 尤其是含左炔诺孕酮的口服避孕药 (LNG) 相比的实际使用避孕效果。

方法：前瞻性、非干预性队列研究, 包括两个主要暴露组和一个暴露亚组：DNG/oEV 和 oCOC 的新使用者, 亚组为LNG。在一项计划的次要分析中, 调查了妊娠结局, 包括避孕失败。评估了年龄、产次和 OC 类型的影响。

结果：对30098例COC使用者进行随访, 共发现68362例女性年 (WY) 口服避孕药接触时间, 287例意外怀孕。欧洲人群的总体避孕失败率为0.4次/100 WY (95%可信区间, 0.4-0.5)。与对照组相比, DNG/oEV的避孕失败率更低。当研究人群仅限于18-35岁的女性时, 这一差异得以维持；该人群中的珍珠指数 (PI) 为0.37 (95%可信区间0.24-0.54), LNG为0.76 (95%可信区间0.56-1.01)。经年龄、产次、吸烟和体重指数校正后, 与oCOC和LNG相比, DNG/oEV的危险比 (HRs) 分别为0.7 (95%可信区间, 0.5-0.98, p = 0.04) 和0.5 (95%可信区间, 0.3-0.8, p < 0.01)。25岁或25岁以下妇女的相应校正HRs分别为0.6（95%可信区间0.4-1.1）和0.4（95%可信区间0.2-0.8）。

结论/讨论：经年龄、产次、使用者状态和吸烟等因素调整后, DNG/oEV 的避孕效果优于oCOC, 尤其是 LNG-COC。

Keywords:

• Prospective cohort study
• active surveillance
• dienogest
• oestradiol valerate
• pearl index
• contraceptive effectiveness

Acknowledgements

The authors would also like to highlight the contributions of numerous colleagues who were responsible for the field work in the individual countries, management of the study database and validation of patient-reported adverse events. The results of this publication would not be possible without their unseen and tireless work.

Disclosure statement

The study was funded by a manufacturer of hormonal contraceptives. The study was supervised by an independent Safety Monitoring and Advisory Council with full authority over the study (including study protocol, protocol amendments, data analysis and stopping the study). The funder had no access to the source data and did not participate in designing the study, analysing the data, preparing or reviewing this publication.

Registration number at the clinical trials registry of the US National Library of Medicine: NCT01009684 (note: this is not a clinical trial).

Additional information

Funding

The study was funded by an unrestricted grant from Bayer AG.