Venous thromboembolism during pregnancy: Trends, incidence, and risk patterns in a large cohort population

To determine the incidence and risk factors for pregnancy-associated venous thromboembolism (VTE).

An observational retrospective study was conducted using data from 452 176 live births between the years 2010 and 2019. The study group consisted of women who were diagnosed with VTE during pregnancy or the postpartum period. The exclusion criteria included women who purchased anticoagulant drugs during pregnancy or postpartum. The hazard ratios (HRs) of VTE per week of each trimester and the postpartum period were calculated.

A total of 421 125 live births were included in the study. Among the study population, 302 cases (0.71 cases/1000 pregnancies) were diagnosed with VTE during pregnancy and postpartum. The overall rates of diagnosis did not change significantly during the study period but followed a declining trend in the postpartum period. The highest risk of VTE was found to be during the third trimester (HR 0.002% per week, 95% confidence interval [CI] 0.0016-0.0023), while the lowest rate was during the postpartum period (HR 0.0007% per week, 95% CI 0.0004-0.0011).

Pregnancy and the puerperium are well-established risk factors for VTE. The present study demonstrates a declining trend in the risk and incidence of VTE during the postpartum period, which can be explained by a liberal and effective VTE prevention policy.