(760) High rates of venous thromboembolism among deliveries complicated by cancer

Objective: Cancer increases the risk of developing venous thromboembolism (VTE) four to seven fold, and pregnancy separately increases risk of VTE by four to five fold. Our objective was to estimate the risk of VTE among patients delivering with a cancer diagnosis.

Study Design: We performed a retrospective cohort study using data from the Nationwide Readmissions Database (NRD), from October 2015 through December 2019, an all-payor database that comprises over 60% of hospitalizations within the United States. Patient demographic information and diagnosis codes were used to identify delivery hospitalizations, cancer diagnoses, and VTE, both during delivery hospitalizations and subsequent inpatient encounters. Primary outcome was VTE incidence at 42 and 330 days, which was compared between patients with and without cancer diagnoses. Secondary analysis performed stratifying by common cancer diagnoses. We compared outcomes using Cox proportional hazards models.

Results: Over the study period, we included 8,004,184 delivery hospitalizations(weighted national estimate, 14,995,112) of which a weighted estimate of 8,574(0.06%) had a diagnosis of cancer during pregnancy. When comparing the cancer cohort to the non-cancer cohort, individuals with cancer were more likely to be over the age of 35 and have higher rates of comorbid conditions(Table 1). The incidence of VTE at 42 days and 330 days among cancer-associated deliveries was 1.2% and 2.3% respectively, versus 0.11% and 0.14% for patients without cancer(Figure 1A). This finding was significant both unadjusted(hazard ratio: 14.71, 95%CI 11.44,18.92) and with adjustment for age, socioeconomic and hospital characteristics, and comorbidities(hazard ratio: 7.37, 95%CI 5.74,9.49). Further stratification by common cancer diagnoses demonstrated elevated risk of VTE across a range of cancer diagnoses(Figure 1B).

Conclusion: Cancer in pregnancy confers an excess thromboembolic risk extending well beyond the immediate postpartum period. Further study is needed to identify optimal VTE prophylactic strategies for this unique population.