Preferential streaming of the ductus venosus and inferior caval vein towards the right heart is associated with left heart underdevelopment in human fetuses with left-sided diaphragmatic hernia.

Objective: Left heart underdevelopment is commonly observed in fetuses with left diaphragmatic hernia. This finding has been attributed to compression of the left atrium by herniated abdominal organs, redistribution of fetal cardiac output and/or low pulmonary venous return. As preferential right or left heart underdevelopment is usually not a feature of right diaphragmatic hernia, we searched for an alternative mechanism.