Fig. 9From: Towards more accurate measurement of edge to os distance in low-lying placenta using three dimensional transvaginal ultrasound: an innovative techniqueAccurate measurement of EOD from the center of IO to the nearest point of lower placental edge (red line, a). When shifted farther from the placental edge, the EOD is longer (blue line, b). When shifted nearer to placental edge, the EOD is shorter (green line, c). P: Placenta; IO: Internal osBack to article page