【Abstract】 Objective To compare the value of transabdominal color doppler ultrasonography (TACDU) with transvaginal color doppler ultrasonography (TVCDU) in diagnosis o£ vasa previa. Methods 31 pregnant women's medical records due to clinical suspicion o£ vasa previa delivery mode to choose cesarean section were analyzed. TACDU or TVCDU were performed sequentially before delivery. The results o£ operation and pathology were taken as the gold standard for diagnosis. The sensitivity, specificity and accuracy o£ the two methods were compared. Results The sensitivity (96. 0% & 88.0%), specificity (83. 0% & 50.0%) and accuracy (93. 50% & 80.6%) o£ TVCDU were significantly different from that o£ TACDU. Six cases were non-vasa previa, including 3 cases of umbilical cord presenting, 2 cases o£ maternal cervical dilated vein and one case of umbilical cord prolapsed. 25 cases were vasa previa including 15 cases with sail placenta, 6 cases with accessory placenta, 3 cases with twin-leaf placenta, and 1 case with marginal insertion o£ umbilical cord placenta. Conclusion Compared with TACDU, TVCDU has higher sensitivity, specificity and accuracy. Reasonable selection o£ the two diagnostic methods can improve the efficiency of vascular pre diagnosis.