BACKGROUND AND EPIDEMIOLOGY
What characteristics increase the risk for venous thromboembolism (VTE)?
Are there ways to prevent VTE during pregnancy? Who are candidates for prophylaxis?
What are the symptoms of VTE?
How should a person with symptoms of VTE be evaluated?
What is the treatment for VTE in pregnancy?
A 36-y.o. G1P1 delivered 3 weeks ago via C-section. She calls the on call doctor to report worsening shortness of breath. She recently noticed that her left low leg is swollen, and she feels pain in the calf when she walks.
VTE is a major contributor to maternal morbidity and mortality in the United States.1 The risk of VTE during pregnancy and the postpartum period is substantially increased compared to the nonpregnant state.2 Deep venous thrombosis (DVT) accounts for approximately three-quarters of thromboembolic events in pregnancy, with pulmonary embolism cases being the remainder. As there is limited high-quality data on which to base the evaluation, treatment, and prevention of VTE in the obstetric population, recommendations are often extrapolated from the nonobstetric literature.
Physiologic changes in pregnancy, such as impaired venous return due to hormonal and structural factors, as well as an increase in procoagulant factors, amplify the propensity for VTE. Factors VII, VIII, X, and XII, as well as von Willebrand factor (VWF), are all increased, as is fibrinogen.3
The elevated risk for VTE begins in the first trimester, although the risk appears to be greatest in the postpartum period.4 One theory for the increased risk during the postpartum period is that endothelial damage (the third component of Virchow's triad) occurs during delivery. While the first 6 weeks postpartum appears to confer the greatest risk, recent data suggests that a small increase in risk remains until 12 weeks after delivery.5
A personal history of previous VTE is the most significant risk factor for developing the condition in pregnancy. Approximately 15% to 25% of VTE cases in pregnancy are recurrent.6 The magnitude of risk for recurrent VTE during pregnancy depends on the circumstances surrounding the initial VTE and the presence of a thrombophilia. Aside from pregnancy, other notable risk factors that have been described include surgery (including cesarean delivery), prolonged immobility, air travel, obesity, age, smoking, and malignancy.
In addition, inherited or acquired thrombophilias are associated with varying degrees of risk for VTE. Those inherited thrombophilias that carry the greatest risk of developing VTE for patients are antithrombin III deficiency, homozygous Factor V Leiden or prothrombin gene mutations, or compound heterozygosity with both Factor V Leiden mutation and prothrombin gene mutation. Protein C and S deficiencies, as well as heterozygosity for Factor V Leiden or the prothrombin gene, confer a lesser degree of risk.