Preeclampsia and Long-Term Risk of Venous Thromboembolism

IMPORTANCE: As venous thromboembolism (VTE) remains one of the leading causes of maternal mortality, identifying women at increased risk of VTE is of great importance. Preeclampsia is a pregnancy-induced hypertensive disorder with generalized endothelial dysfunction. Some studies suggest that preeclampsia is associated with an increased risk of VTE, but much controversy exists. OBJECTIVE: To examine the association between preeclampsia and the risk of VTE during pregnancy, during the puerperium, and after the puerperium. DESIGN, SETTING, AND PARTICIPANTS: This observational cohort study used Danish nationwide registries to identify all eligible primiparous women who gave birth in Denmark from January 1, 1997, to December 31, 2016. The women were followed up from primiparous pregnancy to incident VTE, emigration, death, or the end of the study (December 31, 2016). Statistical analyses were carried out from January to May 2023. EXPOSURE: Preeclampsia during primiparous pregnancy. MAIN OUTCOMES AND MEASURE: The main outcome was incident VTE, and the secondary outcome was all-cause mortality. RESULTS: A total of 522 545 primiparous women (median age, 28 years [IQR, 25-31 years]) were included, and 23 330 (4.5%) received a diagnosis of preeclampsia. Women with preeclampsia were of similar age to women without preeclampsia but had a higher burden of comorbidities. During a median follow-up of 10.2 years (IQR, 5.2-15.4 years), preeclampsia was associated with a higher incidence of VTE compared with no preeclampsia (incidence rate, 448.8 [95% CI, 399.9-503.5] vs 309.6 [95% CI, 300.6-319.9] per 1000 patient-years, corresponding to an unadjusted hazard ratio [HR] of 1.45 [95% CI, 1.29-1.63] and an adjusted HR of 1.43 [95% CI, 1.27-1.61]). When stratified according to the subcategories of VTE, preeclampsia was associated with an increased rate of deep vein thrombosis (unadjusted HR, 1.51 [95% CI, 1.32-1.72] and adjusted HR, 1.49 [95% CI, 1.31-1.70]) as well as pulmonary embolism (unadjusted HR, 1.39 [95% CI, 1.09-1.76]; adjusted HR, 1.36 [95% CI, 1.08-1.73]). These findings held true in landmark analyses during pregnancy, during the puerperium, and after the puerperium. CONCLUSIONS AND RELEVANCE: This cohort study suggests that preeclampsia was associated with a significantly increased risk of VTE during pregnancy, during the puerperium, and after the puerperium, even after thorough adjustment. Future studies should address how to improve the clinical management of women with a history of preeclampsia to prevent VTE.