Racial and ethnic differences in the risk of postpartum venous thromboembolism: a population‐based, case‐control study

Summary Background Venous thromboembolism (VTE) is a major contributor of maternal morbidity and mortality. Whether maternal race/ethnicity is associated with the risk of postpartum VTE remains unclear. Methods and Results We conducted a population‐based, case‐control study in Washington State, from 1987 through 2011. Cases comprised all women with selected International Classification of Diseases, Ninth Edition, Clinical Modification codes for hospitalized VTE within 3 months post‐delivery. Controls were randomly selected postpartum women who did not experience a VTE. Characteristics of women and their deliveries were ed from birth certificates. Using logistic regression models, we compared the risk of postpartum VTE in black, Asian, and Hispanic women with that in non‐Hispanic white women, after adjustment for maternal characteristics (age, body mass index, parity, education), pregnancy complications, and delivery methods. Results Our study comprised 688 cases and 10 246 controls. Among controls, the mean age and body mass index were 27.5 years and 26.3 kg m−2, respectively. Compared with white women, black and Asian women had a greater and lower risk of postpartum VTE (adjusted odds ratio [OR] 1.50, 95% confidence interval [CI] 1.10–2.04 and OR 0.67, 95%CI 0.48–0.94, respectively). A lower risk was present in Hispanic women (adjusted OR 0.80, 95% CI 0.61–1.06) but was not statistically significant. In subgroup analyses, we observed an increased risk for black compared with white women among women who delivered via cesarean section (OR 2.03, 95% CI 1.34–3.07) but not among vaginal deliveries (OR 1.03, 95% CI 0.61–1.74). Conclusions Maternal race/ethnicity is associated with the risk of postpartum VTE, independently of other risk factors, and should be considered when assessing the use of thromboprophylaxis after delivery.