Vein 2 Worlds Collide: May-Thurner Syndrome and Oral Contraceptive Pill Use Precipitating Deep Vein Thrombosis in an Otherwise Healthy Patient.

May-Thurner syndrome (MTS) is a developmental anatomical variant in which the right common iliac artery compresses the left common iliac vein against the underlying lumbar vertebral body. This compression leads to endothelial injury, venous stasis, and progressive luminal narrowing, significantly increasing the risk of left-sided iliofemoral deep vein thrombosis (DVT). Combined oral contraceptives containing ethinyl estradiol are known to increase the risk of DVT, particularly during the initial months of use or during dose changes, with thrombotic risk persisting for up to 10 to 12 weeks after discontinuation. We present the case of a 34-year-old previously healthy female with no significant past medical history who presented with left leg swelling and lower abdominal discomfort. She had intermittently used a combined estrogen-containing oral contraceptive pill, discontinued 2 weeks prior to presentation. Imaging confirmed extensive DVT, and computed tomography venography revealed classic features of MTS, with compression of the left common iliac vein by the right common iliac artery. This case underscores the importance of evaluating structural etiologies in young patients and emphasizes the synergistic risk between hormonal and anatomical factors in precipitating a DVT. Timely diagnosis and targeted management were essential to achieving a favorable outcome.