<prompt> The diagnostic feature of congenital diaphragmatic hernia on prenatal ultrasonography is -A cyst behind the left atriumMediastinal shift with normal hea axisPeristalsis in the thoracic cavityAbsence of gas bubble under the diaphragm  <response>: Ans. is c ie. Peristalsis in the thoracic cavity The sonographic diagnosis of fetal CDH relies on the visualisation of abdominal organs in the chest. Other pointers may be absence of a normally positioned stomach, mediastinal displacement, small abdominal circumference and polyhydramnois. 