The case of a 26-year-old woman who was 23 weeks pregnant is described; the patient presented, on a weekend, to the emergency department (ED) with left groin pain. There were few clinical signs of deep venous thrombosis (DVT) but ED ultrasound (US) showed a left external iliac vein thrombus. This is a new technique in the ED. Not only does this case show the importance of using this technique in the ED, but it also shows the importance of correct training in how to examine for thrombus in the external iliac vein in the pregnant patient. The patient was admitted to the hospital and started on low-molecular-weight heparin. A formal radiology department US performed the next week confirmed the diagnosis of DVT.