Common iliac vein stenosis: A risk factor for oral contraceptive-induced deep vein thrombosis

Objective: The objective of the study was to determine whether women with significant left common iliac vein stenosis who also use combined oral contraceptives (COCs) have a combined likelihood of deep vein thrombosis (DVT) greater than each independent risk. Study Design: This was a case-control study comparing 35 women with DVT against 35 age-matched controls. Common iliac vein diameters were measured from computed tomography and magnetic resonance imaging. Logistic regression modeling was used with adjustment for risk factors. Results: DVT was associated with COC use (P =.022) and with increasing degrees of common iliac vein stenosis (P =.004). Compared with women without venous stenosis or COC use, the odds of DVT in women with a 70% venous stenosis who also use COCs was associated with a 17-fold increase (P =.01). Conclusion: Venous stenosis and COC use are independent risk factors for DVT. Women concurrently exposed to both have a multiplicative effect resulting in an increased risk of DVT. We recommend further studies to investigate this effect and its potential clinical implications.