Incidence of Pregnancy-Associated Venous Thromboembolism: Second Nationwide Study

Pregnancy is a transient risk factor for venous thromboembolism (VTE). This second nationwide study aimed to inspect trend changes in the incidence rate of pregnancy-associated VTE (PA-VTE) during the study period (2014-2018) compared with that reported in a previous study (2006-2010).

Using the Korean Health Insurance Review and Assessment Service database, we retrospectively identified all PA-VTE events using both diagnostic and medication codes.

Of the 124,228 VTE events, 510 (0.4%) cases of PA-VTE were identified in 499 women (median age: 34 years; range: 20-49 years). The incidence rate of PA-VTE/10,000 deliveries (PA-VTE/10⁴D) in this second study (2.62) was 3.2 times higher than that in the first study (0.82). In the second study, the PA-VTE/10⁴D ratio of women in their 40s (5.46) was three times higher than that of women in their 20s (1.80) (relative risk: 3.03; 95% confidence interval: 2.04-4.51; p < 0.01). The incidence rate for women in their 40s in the second study was 2.3 times higher than that in the first study. PA-VTE/10⁴D cases occurred more frequently in multiparous than in primiparous women, in cesarean section cases compared with vaginal delivery, and in multiple rather than single pregnancies. Most PA-VTE cases occurred during the postpartum period (321/510, 62.9%), of which pulmonary embolism was the most frequently occurring type (231/321, 72%).

Advanced maternal age, cesarean section, multiparity, and multifetal pregnancies increased the risk of PA-VTE. Obstetricians need to be cautious of VTE, particularly during the postpartum period, in high-risk pregnant patients.