May-Thurner syndrome resulting in acute iliofemoral deep vein thrombosis during the second trimester of pregnancy.

Described is a 27-year-old pregnant woman with May-Thurner syndrome who experienced extensive pelvic and lower extremity thromboses during the antepartum period. The patient was referred for a symptomatic deep venous thrombosis at 23 weeks of gestation. Ultrasonography demonstrated a massive thrombus in the left iliofemoral vein. Heparin was given intravenously. Due to the possibility of pulmonary embolism during or immediately after delivery, a temporary inferior vena cava filter was inserted at 36 weeks of gestation. Labor was induced at 37 + 5 weeks of gestation; labor proceeded uneventfully and a male infant was born. Postpartum computed tomography (CT) demonstrated compression of the left common iliac vein by the right common iliac artery and lumbar vertebra. CT venogram demonstrated poor flow through the common iliac vein and well-developed collateral vessels. Critical stenosis at the origin of the left common iliac vein was consistent with a diagnosis of May-Thurner syndrome.