Venous thromboembolism incidence among patients recommended for pharmacologic thromboembolism prophylaxis after cesarean delivery in selected guidelines.

In a cohort of 1 235 149 cesarean deliveries, VTE incidence was 2.1 per 1000 deliveries at 330 days following delivery (95% confidence interval: 2.0-2.2). Proportions of patients that would be recommended for pharmacologic prophylaxis ranged from 0.2% in 2018 ASH guidelines to 73.4% in 2015 RCOG criteria. Among groups considered at elevated risk for VTE for which pharmacologic prophylaxis would be recommended, VTE incidence varied from 35.2 per 1000 deliveries based on 2018 ASH criteria to 2.5 per 1000 in 2015 RCOG criteria. In a large cohort of cesarean deliveries in the United States, application of different risk stratification guidelines identified widely different proportions at risk of VTE following delivery, with implications for being categorized as having elevated risk.