Hormonal Contraception and Venous Tromboembolism: Recent Epidemiological Data

Overview

Objective:
To sum up the results of studies published between 1996 and 2000 on the venous thromboembolism (VTE) risk at combined oral contraceptives users.Design: Review of literature.Setting: 1st Department of Obstetrics and Gynecology, Masaryk University, Brno, Czech Republic.Methods: Summary of results of substantial studies published on this topic. Studies were identified by Medline database search.Results: Four important epidemiological studies published at 1995 and 1996 (WHO, Spitzer et al., Jick et al., Bloemenkamp et al.) demonstrated two fold increased risk of VTE at users of third generation OCs in comparison with second generation OCs. Publication of these studies was followed by critic based on their possible methodological weaknesses (prescribing bias, „healthy user“ effect, refferal bias etc.). Other epidemiologists confirmed results of these studies and excluded the possibility of systemic biases. Pathophysiological mechanisms that could explain the different risks were also found. Jick’s analysis of GRPD published in 2000 also confirmed the results from 1995 and 1996.Conclusion: The different risk of VTE at users of oral contraceptives with different progestins probably exists. However, the relative risks of VTE demonstrated in recent studies are low.

Key words:
combined oral contraceptives, venous thromboembolism