Objective: Venous thromboembolism (VTE) is a leading cause of maternal morbidity and mortality in the United States among women undergoing cesarean section. Specific factors associated with VTE during cesarean delivery hospitalization have not been comprehensively assessed. This study sought to identify risk factors and assess trends in VTE in a large population of women undergoing cesarean delivery in the United States.
Methods: VTE incidence was analyzed in women aged 12-55 who underwent cesarean section in United States hospitals using the Nationwide Inpatient Sample database. The study included discharge records from January 1, 2005 through December 31, 2015. Sample population data were weighted to provide national estimates. The study population was identified using codes from the International Classification of Disease, Ninth and Tenth Revisions (ICD-9 and ICD-10) for cesarean delivery; these codes were also used to identify diagnosis of VTE and various comorbidities. The primary outcome was incidence of VTE. Secondary outcomes included temporal trends of VTE and association of patient characteristics and outcomes with VTE incidence. Chi-squared tests and logistic regressions were used for univariate and multivariate analysis, respectively.
Results: Of 14,071,941 cesarean delivery hospitalizations in the study period, 9,663 (0.07%) had VTE. When comparing patients with and without VTE, a higher proportion of patients with black race (19.65% vs 12.72%, p<0.0001) and advanced maternal age (AMA) (24.42% vs 19.75%, p<0.0001) were in the VTE group. With multivariate analysis including age, race, teaching status, and various patient comorbidities, of the two previously identified groups only AMA was independently associated with VTE (OR 1.17 [1.02-1.36], p=.029). Chronic patient comorbidities independently associated with VTE included the following: thrombophilia (OR 6.94 [4.83-9.97], p<.001), history of VTE (OR 3.76 [2.35-6.01], p<.001), cardiovascular disease (OR 3.36 [2.64-4.26], p<.001), disseminated intravascular coagulopathy (OR 3.34 [2.28-4.26], p<.001), and sickle cell disease (OR 2.99 [1.75-5.13], p<.001). Pregnancy-related comorbidities or associated procedures independently associated with VTE included puerperal infection (OR 7.82 [6.48-9.43], p<.001) and blood transfusion (OR 3.28 [2.62-4.11], p<.001). Age-adjusted incidence of VTE decreased over the study period (p<.0001).
Conclusion: Patients with AMA and/or black race appear to be at higher risk of VTE during cesarean delivery hospitalization. Only AMA was independently associated with VTE when evaluating both of these subgroups. Prospective study is warranted to best optimize thromboprophylaxis in women undergoing cesarean delivery.