Unintended pregnancy in users of nomegestrol acetate and 17β-oestradiol (NOMAC-E2) compared with levonorgestrel-containing combined oral contraceptives: final results from the PRO-E2 study

Eur J Contracept Reprod Health Care. 2021 Oct 15:1-7. doi: 10.1080/13625187.2021.1988923. Online ahead of print.

ABSTRACT

OBJECTIVE: To assess and compare the risk of unintended pregnancy in NOMAC-E2 users with levonorgestrel-containing COC (COC_LNG) users in clinical practice.

STUDY DESIGN: In this observational study, new users¹ of NOMAC-E2 and COC_LNG were recruited in Europe, Australia, and Latin America and followed for up to 2 years. Unintended pregnancy was expressed by the Pearl Index (contraceptive failures per 100 women-years [WY]), crude hazard ratios (HR_crude) and adjusted hazard ratios (HR_adj).

RESULTS: Overall, 44,559 and 46,754 users were recruited to the NOMAC-E2 and COC_LNG user cohorts, respectively. There were 64 unintended pregnancies in NOMAC-E2 users (0.15 per 100 WY; 95% CI, 0.11-0.19) and 200 in COC_LNG users (0.41 per 100 WY; 95% CI, 0.35-0.47). The unintended pregnancy risk was statistically significantly lower in the NOMAC-E2 cohort (p<.0001) compared to the COC_LNG user cohort. The HR_adj of NOMAC-E2 vs COC_LNG was 0.45 (95% CI, 0.34-0.60; adjusted for age, body mass index, gravidity, COC user status, education level).

CONCLUSIONS: NOMAC-E2 demonstrated superior contraceptive effectiveness compared to COC_LNG, likely due to the comparatively short hormone-free interval and possibly reinforced by the long half-life of NOMAC.

PMID:34651535 | DOI:10.1080/13625187.2021.1988923