Air travel during pregnancy and the risk of venous thrombosis.

BACKGROUND: Pregnancy and air travel independently increase the risk of venous thrombosis. However, there is a lack of data regarding the added risk, if at all, of thrombosis after air travel during pregnancy. OBJECTIVE: This study aimed to determine the potential added risk of venous thromboembolism among pregnant women who traveled by air. STUDY DESIGN: This was an observational retrospective study using data from 452,663 live births between the years 2010 to 2019. The study group consisted of women who flew during pregnancy. Data of pregnant women who flew during pregnancy were compared with that of pregnant women who did not fly during pregnancy. The primary outcome was venous thromboembolism during pregnancy and in the postpartum period. A case of venous thromboembolism was deemed related to air travel only if it occurred up to 8 weeks after the return flight (exposure time). Propensity score weighting Poisson regression was calculated to assess the effect and to control selection biases. Risk per day was calculated. RESULTS: Overall, 421,125 live births were included. Of those cases, 33,674 (8%) had traveled by air during pregnancy (study group), and 387,451 (92%) did not (control group). There were 6 cases of venous thromboembolism after a flight that occurred during the exposure time of 8 weeks and 285 cases of venous thromboembolism in the control group (0.05% vs 0.07%; P=.158). When the propensity weighting Poisson regression was calculated as risk per day, there was a significantly increased risk between the study and control groups (0.00031% vs 0.00022%; hazard ratio, 1.406; P=.005). CONCLUSION: The overall risk of venous thromboembolism after air travel is low; however, our study found that the risk of venous thromboembolism during pregnancy is increased by air traveling.

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

OBJECTIVE: To determine the incidence and risk factors for pregnancy-associated venous thromboembolism (VTE). METHODS: 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. RESULTS: 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). CONCLUSION: 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.