Anatomic Distribution of Deep Vein Thrombosis in Pregnancy

ABSTRACT There is a high risk of pulmonary embolism (40%–50%) in patients with proximal deep vein thrombosis (DVT), and maternal morbidity and mortality may be high among women with untreated or unrecognized embolism. Evidence exists that the anatomic distribution of DVT in nonpregnant and pregnant patients may differ, with important clinical implications for optimizing diagnostic imaging protocols. In nonpregnant patients, prospective studies have shown that most DVTs of the lower extremity develop in the calf vein and further extend proximally; the majority of nonpregnant patients with a proximal thrombosis have involvement of the calf veins, and isolated proximal vein thrombi are uncommon. The typical anatomic distribution of DVT in pregnant patients is less clear. The primary aim of this systematic review of the medical literature was to determine the anatomic distribution of DVT of the lower extremity in symptomatic pregnant patients. Previously published studies of cohorts of pregnant women with DVT were examined using MEDLINE (1966–2009), Embase (1980–2009), and the Cochrane Library. Data were extracted from articles that were case series or observational cohorts of 3 or more participants, in which a DVT was diagnosed using objective techniques in unselected or consecutive pregnant women. In all, 6 articles meeting the criteria for inclusion were identified from an initial list of 1098 titles. A total of 124 women had been given a diagnosis of DVT; venography was used in 55 patients, whereas compression ultrasonography was the primary mode of diagnosis for 69 patients. The most common site for acute DVT was the proximal veins without involvement of calf veins (87/122; 71%); in 56 (64%) of these 87 patients, thrombosis was restricted to the iliac and/or femoral vein. Overall, 84 (88%) of the 96 patients (for whom the affected side was reported) had involvement of the left leg. These findings strongly suggest a difference in the anatomic distribution of DVT in pregnant versus nonpregnant women. The data confirm previous findings that, in contrast to the situation in nonpregnant individuals during pregnancy, most DVTs are proximal and restricted to the femoral or iliac veins, and most are on the left side.