A 30-year-old woman in her last trimester of pregnancy suddenly develops massive swelling of the left lower extremity. Which of the following would be the most appropriate workup and treatment at this time

Duplex ultrasound is the diagnostic modality of choice for detection of infrainguinal deep venous thrombosis (DVT). Although venography is the gold standard, it is no longer routinely used, given the risks of local (thrombosis, pain) and contrast-related (allergic reaction, renal failure) complications. Impedance plethysmography, which measures changes in volume in the lower extremity as related to blood flow, is also used infrequently due to the superiority of duplex scanning in detecting DVTs. In pregnant women, anticoagulation for treatment of DVT is achieved with heparin, which does not cross the placenta, rather than warfarin, which is associated with the risk of spontaneous aboion and bih defects. The vena caval filter is not indicated because there is no contraindication to heparin therapy and no evidence of failure of anticoagulation therapy (pulmonary embolus in the face of adequate anticoagulation).