Paper Presented to the Peripheral Vascular Surgery Society - 20th Annual Winter Meeting
Incidence and Characteristics of Venous Thromboembolic Disease During Pregnancy and the Postnatal Period: A Contemporary Series

Presented at the 20th Annual Winter Meeting of the Peripheral Vascular Surgery Society, Vail, CO, January 29-31, 2010.
https://doi.org/10.1016/j.avsg.2010.04.003Get rights and content

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.

Introduction

The pregnancy and postnatal periods are associated with an increased risk of thromboembolic disease, particularly deep venous thrombosis (DVT) and pulmonary embolism (PE). The proposed mechanism has not been yet completely established; however, it is believed to arise from increased venous stasis caused by compression from the gravid uterus and hemostatic imbalance secondary to increased plasma levels of pregnancy-related hormones.1 Venous thromboembolic disease is a leading cause of maternal morbidity, and pulmonary embolus is the most common cause of maternal mortality in the developed world.2 Therefore, timely identification of patients with DVT and PE is extremely important. Although the overall risk of a venous thromboembolic event (VTE) is small, pregnant and postpartum patients have a 5 times greater chance of developing an event as compared with nonpregnant women of similar age.3

Numerous studies have examined the incidence and risk factors of venous thromboembolic disease in pregnancy.3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 Commonly accepted risk factors predisposing women to venous thrombosis during the puerperal period include age over 35, obesity (body mass index >30 kg/m2), multiparity (>3 prior deliveries), personal history of DVT or PE, inherited thrombophilia, surgery or cesarean delivery, smoking, and hormonal therapies.15 Other associated risk factors include gestational diabetes, placental abruption, and eclampsia.14

The goal of our study was to determine whether the incidence of DVT and pulmonary embolus has changed, using current diagnostic modalities in a contemporary series of patients. Prior studies have found a much higher incidence of DVT than pulmonary embolus.3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 These studies, however, were primarily conducted in the 1980s and 1990s using older diagnostic tests to examine for pulmonary embolus. Pulmonary embolus was typically diagnosed using ventilation perfusion scans. The established sensitivity of ventilation perfusion scans is 65% in modern series.16 Over the past 10 years, computerized tomographic angiography (CTA) for the diagnosis of PE has evolved into the test of choice for diagnosis of PE, with a significantly higher sensitivity of 83%.17 CTA has been used routinely at our institution for the diagnosis of pulmonary embolus for the past decade, including those in pregnant patients. Duplex ultrasonography, however, has been well established for the diagnosis of DVT for over 20 years. Its sensitivity and specificity is more than 90% for diagnosing proximal vein thrombosis in pregnant patients.18

Section snippets

Materials and Methods

This retrospective study was conducted at two affiliated urban tertiary care facilities. Institutional review board approval was obtained from the participating institutions. Women with a diagnosis of DVT or pulmonary embolus during pregnancy or the first 3 months thereafter, were selected through hospital discharge International Classification of Disease Codes, editions 9 and 10 between June 1, 2003 and June 30, 2008. The total number of pregnancies during this period was 33,311. Only patients

Results

During the period from June 1, 2003 to June 30, 2008, there were 33,311 deliveries. The total number of vaginal deliveries was 23,753 (71.3%) and the total number of cesarean deliveries was 9,558 (28.7%). Of these, a total of 74 patients (0.22%) had a VTE, or two in 1,000 pregnancies. There were 40 incidents of DVT (0.12%) and 37 of PE (0.11%). Six patients (0.02%) had simultaneous DVT and PE at the time of diagnosis. More than half of the events (38; 51.6%) occurred in the postpartum period.

Discussion

Pregnancy and the postpartum period place women of reproductive age at risk for development of DVT and PE. The two underlying mechanisms hypothesized to play a role during pregnancy are hormonal induced hypercoagulability and mechanical compression from the gravid uterus.19 Normal pregnancy results in an increased level of clotting factors VII, VIII, X, von Willebrand Factor, and higher concentrations of fibrinogen.20 In addition, anticoagulant proteins decrease. Free levels of protein S

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