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Updated: Jan 15, 2026

A Multicenter MRI Protocol for the Evaluation and Quantification of Deep Vein Thrombosis
Published on: June 2, 2015
Risk of venous thromboembolism associated with chlormadinone acetate- and levonorgestrel-containing combined oral
P De Corte1, M Klinghardt1, A Bauerfeind1
1Berlin Center for Epidemiology and Health Research, Berlin, Germany.
Objective:
We assessed the risk of venous thromboembolism (VTE) risk of chlormadinone acetate (CMA) 2 mg/ethinylestradiol (EE) 30 µg as opposed to levonorgestrel (LNG) 0.15 mg/EE 30 µg.
Study Design:
We pooled data from four comparable, large, observational studies in a dataset comprising new users of combined oral contraceptives (COC). Individuals with a personal history of VTE were excluded. Incidence rates of confirmed VTE were summarized. Cox models were performed to calculate crude and adjusted hazard ratios (HRs).
Results:
We identified 31,379 COC users exposed to either CMA 2 mg/EE 30 µg or LNG 0.15 mg/EE 30 µg, contributing to 59,167 women-years. Sixty VTE were reported. VTE incidence rates were comparable between CMA- and LNG-cohorts (9.8/10,000 woman-years [WY]; 95% confidence interval [CI]: 6.36-14.50 vs. 10.38/10,000 WY; 95% CI: 7.23-14.44, respectively). The HR was 1.25 (95% CI: 0.72-2.14) after adjusting for age, BMI, family history of VTE and current duration of use.
Conclusion:
Within the general limitations of observational research, we conclude that this study and its contributing studies provide a robust basis to compare the risk of VTE in users of CMA 2 mg/EE 30 µg to those of LNG 0.15 mg/EE 30 µg. While we found an HR > 1 for CMA 2 mg/EE 30 µg compared to LNG 0.15 mg/EE 30 µg, the increase was non-significant, and the absolute risk increase remained small and in line with previous studies.
Implications:
No significant differences were found regarding the risk of VTE between users of CMA- and LNG-containing COCs. Incidence rates of VTE were in line with previous findings of VTE incidences across various COCs.
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