Anticoagulant prophylaxis in pregnant women with a history of venous thromboembolism: A systematic review and meta-analysis

Background: Venous thromboembolism (VTE) remains one of the leading causes of morbidity and mortality during pregnancy and the postpartum period. Despite that, the prevention and management of VTEs in pregnant patients is an area of great debate. Objectives: The aim of this systematic review was to evaluate the risk of VTE recurrence during pregnancy for pregnant patients with prior personal history of VTE and the effect of LMWH on such risk. Methods: MEDLINE and EMBASE were searched between January 2000 to December 2022. We included studies that evaluated pregnant patients with previous personal history of VTE and assessed VTE recurrence with or without thromboprophylaxis. A meta-analysis of proportions was done through a Freeman–Tukey transformation using random effect models. Results: 30 studies were included in this systematic review. The studies included 5075 pregnant patients with a previous history of DVT or PE. We found a wide variability in thromboprophylaxis strategies. The estimated pooled proportions of VTE recurrence were 2.5% (95% CI 1.8–3.3) in patients who were consistently on anticoagulation during pregnancy (pre- and post-partum), 4.7% (95% CI 1.8–8.8) in patients who received anticoagulation in the postpartum period only, and 13.6% (95% CI 6.5 to 22.8) in patients who were not on anticoagulation. Conclusions: In patients with a previous VTE history receiving prophylactic anticoagulation (either both pre- and post-partum or post-partum only), the estimates of VTE recurrence were lower than for patients who did not receive prophylaxis, however, a direct comparison was not possible. The optimal thromboprophylaxis strategy remains unknown.