Venous thromboembolism and adverse outcomes in highest thromboembolism risk patients compared with those at lower risk

Abstract

A risk-based institutional protocol for inpatient heparin-based venous thromboembolism prophylaxis in a general obstetrical population previously demonstrated a greater than 2-fold increase in wound hematomas with no change in the frequency of thromboembolism. We sought to compare the rates of thromboembolism and bleeding outcomes in patients at the highest risk for thromboembolism (eg, those with a history of thromboembolism or thrombophilia who require anticoagulation prophylaxis or therapy throughout pregnancy) than low-risk patients. We performed a retrospective cohort study of all deliveries >20 weeks at a single center from 2013-2018. Patients were categorized as high-risk (received outpatient heparin-based prophylaxis or treatment) or low-risk (no outpatient anticoagulation). The primary outcome was newly diagnosed postpartum thromboembolism; the main secondary outcome was wound/perineal hematoma. The outcomes were compared between the high- and low-risk cohorts. Adjusted odds ratios (with 95% confidence intervals) were calculated with the low-risk group as reference. Of 24,303 total deliveries, 395 (1.7%) were high-risk and 23,905 (98.3%) were low-risk. Among the low-risk patients, 8.6% received anticoagulation prophylaxis in accordance with our risk-based inpatient thromboembolism prophylaxis protocol. High-risk patients were more likely to be older and have a higher body mass index, earlier delivery gestational age, medical comorbidities, and pregnancy complications, eg, preeclampsia. Despite outpatient antepartum anticoagulation, high-risk patients had an 11-fold increased risk of thromboembolism (adjusted odds ratio, 11.1 [4.7-26.2]) than low-risk patients. High-risk patients also had significantly more wound/perineal hematomas (adjusted odds ratio, 4.8 [2.7-8.4]), overall wound complications (adjusted odds ratio, 3.0 [2.0-4.4]), blood transfusions, intensive care unit admissions, maternal deaths, and longer maternal lengths of stay. Patients at the highest risk of obstetrical thromboembolism had an 11-fold increased risk of thromboembolism with a more moderate increase (∼5-fold) in postpartum wound and bleeding complications than low-risk patients. This more favorable risk or benefit profile supports current anticoagulation recommendations in high-risk patients.