1B.1 Risk factors and diagnosis of VTE in pregancy

Abstract

Pulmonary thromboembolism is the major cause of maternal death in the UK. In addition to mortality and acute morbidity, these women are also at risk of future deep venous thrombosis (DVT), venous insufficiency and pulmonary hypertension. In pregnancy DVT is usually left sided (85% versus 55% in the non pregnant) and ilio-femoral (72% iliofemoral in pregnancy versus 9% in non pregnant). Furthermnore, VTE can occur at any time in the antenatal period with 50% of events occurring in the first 15 weeks. Previous thrombotic event(s), age, obesity, thrombophilia and operative delivery are arguably the most important risk factors (Table 1). In a ten year review of 650,000 pregnancies in Scotland the incidence of antenatal DVT was greater than postnatal DVT although the rate was higher in the postpartum period. Furthermore, the rate doubled with age over 35 years and also with operative delivery. The pathophysiology of venous thrombosis in pregnancy is associated with the procoagulant changes of pregnancy, venous stasis and trauma to the pelvic veins at delivery. Thus it is not surprising that heritable thrombophilias, including antithrombin (AT), protein C or S deficiencies, factor V Leiden and the prothrombin G20210A, underlie up to 50% of pregnancy related thromboses. Acquired thrombophilic traits such as antiphospholipid antibody syndrome also place the patient at risk. Objective diagnosis is essential when VTE is suspected and duplex ultrasound venography and ventilationperfusion lung scans remain first line investigations. However investigations such as CTPA are increasingly being used for PTE, although they are associated with significant radiation exposure to the maternal breast, CTPA is associated with an even lower dose of radiation to the fetus than VQ scans. Thus, there are particular problems with regard to venous thromboembolic disease in pregnancy and its management, which present a challenge to the obstetric physician.