The natural history of pelvic vein thrombosis on magnetic resonance venography after vaginal delivery

OBJECTIVE: Venous thromboembolism constitutes the leading cause of direct maternal mortality in the developed world. To date, there are no studies using magnetic resonance venography (MRV) to delineate the incidence and natural history of intraluminal filling defects in the postpartum period in patients with low thrombosis risk. STUDY DESIGN: This was a prospective cohort study of women at low thrombosis risk postvaginal delivery undergoing MRV in the early postpartum period. RESULTS: In 30 eligible and consenting participants, independently adjudicated MRV, conducted on a median of postpartum day 1, identified definite thrombosis in 30% (95% confidence interval [CI], 13.6-46.4%) of study participants. All episodes of definite thrombosis were identified in the iliac and ovarian veins. Probable thrombosis was identified in an additional 27% of study participants (95% CI, 10.3-41.7%), and possible thrombosis in an additional 10% (95% CI, 0-20.7%). CONCLUSION: In this group of low-risk postpartum patients, we identified a high prevalence of definite pelvic vein intraluminal filling defects of uncertain clinical significance. This study suggests that some degree of pelvic vein intraluminal filling defect may be a normal finding after uncomplicated vaginal delivery.