Pelvic Magnetic Resonance Venography Reveals High Rate of Pelvic Vein Thrombosis After Cesarean Section

Abstract

Venous thromboembolism (VTE) not only remains the major cause of direct maternal mortality in developed countries worldwide, but reportedly causes more than half of direct maternal deaths in the United States. Although cesarean section increases the risk of pregnancy-associated VTE, postpartum thromboprophylaxis is not uniformly recommended. Magnetic resonance venography (MRV) appears to be a highly sensitive and specific means of detecting deep venous thrombosis (DVT) in the upper and lower extremities. The investigators report preliminary findings of an ongoing randomized, controlled trial that uses MRV to identify pelvic DVT after operative delivery. Observations were made during the run-in phase of a trial of thromboprophylaxis in women at moderate to high risk of DVT based on a family history of VTE or a personal history of superficial phlebitis, current major illness or infection, immobility for longer than 4 days, obesity, or age greater than 35 years. Other risk factors included gross varicose veins, preeclampsia, parity of 4 or more, emergency cesarean section, and extended surgery such as cesarean hysterectomy. The women were assigned to receive or not to receive open-label tinzaparin, a low-molecular-weight heparin, by subcutaneous injection. Two radiologists independently and blindly assessed the MRV studies. Participants included 15 women with a mean age of 33 years. None of them had compression leg ultrasound findings of DVT. The MRV findings were interpreted as showing definite thrombosis in 46% of women, all of whom were asymptomatic. Clots were found chiefly in the iliac veins, although one patient had thrombosis in the common femoral artery. All clots were less than 1 cm in size and only one occluded the affected vein. Nearly half of these moderate- or high-risk women were found to have definite pelvic DVT after cesarean delivery-many more than expected. The clinical significance of this finding remains to be determined. It is possible that pelvic vein thrombosis is a normal finding after cesarean delivery and also that DVT may be present in lower-risk women. MRV would seem to be a useful measure of outcome in studies evaluating postpartum measures intended to prevent DVT.