What is the most common intrathoracic or extracardiac fetal anomaly?
Congenital diaphragmatic hernia (CDH) occurs in 1 of every 2000 to 3000 live births. Up to 90% occur on the left side and can occur posterolaterally as a Bochdalek hernia in 90%, or anteromedially as a Morgagni hernia in 10%.
CDH is diagnosed on US by the demonstration of abdominal contents (stomach, liver, bowel, mesenteric fat), cystic structures, or solid structures within the thorax. The diagnosis is often first suspected when the stomach and/or bowel is seen adjacent to the heart on a standard four-chamber heart view.
Other US findings include peristaltic movements in the chest, contralateral cardiac and mediastinal shift, and a small AC. There is an association with polyhydramnios and pulmonary hypoplasia if fetal swallowing and lung development is impaired due to intrathoracic mass effect.