Incidence and risk factors of venous thromboembolism during postpartum period: a population-based cohort-study.

INTRODUCTION: The awareness of the incidence and timing of postpartum venous thromboembolic events guides the use of thromboprophylaxis. Our aims were to assess the incidence and mortality of venous thromboembolic events and identify its associated risk factors during different postpartum periods.

MATERIAL AND METHODS: A population-based controlled cohort study by combining four large registers in 2001-2011. All women with a recent delivery were identified. The incidence, risk factors and mortality of venous thromboembolic events 0-180 days after delivery were assessed by using all healthy delivered women as the control group. The incidence was compared with that of the nonpregnant women.

RESULTS: Among the 634 292 delivered women, 1169 had venous thromboembolic events 0-180 days postpartum. The incidence of venous thromboembolic events was highest during the first week postpartum: 37-fold compared with nonpregnant women, declining to two-fold immediately after that. Almost half of the venous thromboembolic events occurred between 43 and 180 days postpartum. The incidence of venous thromboembolic events was four-fold compared with that of nonpregnant women. Three venous thromboembolic events-related deaths occurred. Older age, higher body mass index, thrombophilia, multiple pregnancy, gestational diabetes, anemia, chorioamnionitis, threatening premature birth, in vitro fertilization with ovarian hyperstimulation, primiparity, cesarean section, cardiac/renal diseases, and varicose veins were associated with an increased risk for postpartum venous thromboembolic events. The risk remained elevated for 180 days in women with thrombophilia, cesarean section, multiple pregnancy, varicose veins, and cardiac disease.

CONCLUSIONS: The risk of venous thromboembolic events remained elevated compared with that of the nonpregnant women after the usually defined postpartum period (6 weeks). The results might assist in selecting women in need of thromboprophylaxis.