Risks of venous thromboembolism after cesarean sections: a meta-analysis

Abstract

Background: Cesarean sections (CS) are believed to be associated with greater risks of postpartum venous thromboembolism (VTE). Our objective was to systematically review the evidence on this association and on the absolute risk of VTE after CS. Methods: Authors searched PubMed, Embase and conference proceedings from 1980 to 11/2015 for reports on the associations of delivery methods with postpartum VTE and on the incidence of VTE after CS. They excluded studies on thrombophilia or recurrent VTE and restricted to prospective studies when assessing the incidence of VTE. Pooled relative and absolute risks were estimated with random-effects models. Results: search retrieved 28 mostly retrospective observational studies comparing risks of VTE after CS and after vaginal deliveries (VD) (n > 53 000 VTE events), and 32 prospective studies reporting risks of VTE after CS (n = 218 VTE events). Compared with VD, the relative risk of VTE after CS ranged from 1–22, with a meta-analytic odds ratio (OR) of 3.7 (95% CI 3.0–4.6). Adjustment for age and BMI had a marginal influence on the estimated pooled OR. Associations were observed for both elective and emergency CS, with stronger estimates of associations for emergency CS. The pooled incidence was 2.6 VTE/1000 CS (95% CI 1.7–3.5), and was greater in studies with a longer and better follow-up in the postpartum (4.3/1000 CS). Conclusion: The risk of VTE is 4-fold greater after CS than VD, appears independent of other VTE risk factors, and is greater after emergency than elective CS. On average, 3 in 1000 women will develop a VTE after CS.