Objective To explore the two-dimensional and three-dimensional ultrasonographic features of cord-like structures in gravid uterus during the second and third trimester of pregnancy and improve the understanding and accuracy of diagnosis of these disease.Methods The characteristics of two-dimensional and three-dimensional ultrasound imaging and clinical data of 224 cases of intrauterine cord-like echos during the second and third trimester of pregnancy were retrospectively analyzed.Results In this study

among the 224 cases with intrauterine cord-like echo during the second and third trimester of pregnancy，the most common is uterine synechia bands

with 170 cases，which can appear anywhere in the uterine cavity. The number，thickness and shape of intrauterine adhesions could be demonstrated by three-dimensional ultrasound. There were 19 cases of amniotic sheet

which two-dimensional ultrasound showed that the edge of the amniotic membrane extended into the amniotic cavity to form a strip like echo，with free distal end

and three-dimensional ultrasound showed that the amniotic sheet were reflective membrane. There were 12 cases of incomplete mediastinal uterus

which thick septum always located at the bottom or upper part of the uterine cavity. The morphology of septum and its position relationship with placenta attachment could be identified by three-dimensional ultrasound. There were 11 cases of circumvallate placenta，which cord-like echo was detected at the margin of the placenta in two dimensional ultrasound and can be shown as ring-shaped protrusions or local ridge shaped protrusions at the edge of the placenta in three-dimensional pattern. There were 4 cases of chorioamniotic separation

which amniotic membrane exhibits a flapping linear echo

separated from the chorion. On 3D ultrasound

it has an appearance similar to a layer of gauze. There were 2 cases of amniotic cord syndrome

which showed multiple thin and disordered light bands echoing in the uterine cavity

adhering to the fetus

and with unclear boundaries with the fetal limbs in in two dimensional ultrasound. Three dimensional ultrasound shows a disordered membranous structure on the surface of fetal limbs. Conclusion Two-dimensional ultrasound combined with three-dimensional ultrasound can comprehensively observe intrauterine cord-like echo in the second and third trimester of pregnancy，and analyze its different ultrasound imaging characteristics，which is conducive to improving diagnostic accuracy of intrauterine cord-like echo in the second and third trimester of pregnancy.