Incidence and Characteristics of Venous Thromboembolic Disease During Pregnancy and the Postnatal Period: A Contemporary Series

Background: To evaluate the incidence and characteristics of venous thromboembolic events (VTE) associated with pregnancy in a contemporary patient series. Methods: We performed a retrospective review of 33,311 deliveries between June 2003 and June 2008. Patients with objective documentation of a VTE during pregnancy or the 3-month postnatal period were identified from hospital discharge International Classification of Disease Codes edition 9 codes. Diagnosis of deep venous thrombosis (DVT) was largely made by a Duplex ultrasound, whereas pulmonary embolism (PE) was diagnosed by a computerized tomographic angiography (CTA). Results: Of 33,311 deliveries during the study period, 74 patients (0.22%) had a VTE. There were 40 incidents of DVT (0.12%) and 37 of PE (0.11%). DVT involved the iliac veins (6), the femoral or popliteal veins (16), the infrapopliteal veins (17), and the axillary vein (1). Most (57.5%) of the DVTs involved the left lower extremity. Thirty-eight (51.6%) of the VTEs occurred in the postnatal period, and of those 33 (87%) occurred within 1 week of delivery. Most of the postnatal VTEs (68%) were seen in patients who underwent a cesarean section. Among patients with VTE during pregnancy, there were 28% in the first trimester, 25% in the second, and 47% in the third. Events were distributed among maternal age groups as follows: 26% aged 13-24, 50% aged 25-34, and 24% aged 35-54. Of the 35 patients tested for a hypercoagulable disorder, 12 were found to have a positive test result. Five (6.8%) of these 74 patients had a prior history of VTE, with two having a hypercoagulable disorder. In addition, 45 of the 74 patients were on oral contraceptive therapy or received hormonal stimulation therapy before pregnancy. Patients with a VTE during pregnancy were treated with low molecular weight or unfractionated heparin. Most postnatal patients were treated with subcutaneous low molecular weight heparin and coumadin. Six inferior vena cava filters were placed in patients with bleeding complications as a result of anticoagulation. There were no deaths during the study period. Conclusions: Comparing our results with historic controls (DVT: 0.04-0.14% and PE: 0.003-0.04%), the incidence of DVT in pregnancy has not changed significantly. We note, however, that the incidence of pulmonary embolus in our series is higher than previously reported. CTA has been used for the diagnosis of PE since the past decade. The increase in the rate of PE in the current series may be because of the higher sensitivity of CTA when compared with previous diagnostic modalities.