ABSTRACTObjective Prenatal heart adaptations to congenital diaphragmatic hernia (CDH) could help define postnatal outcome. Methods We retrospectively analyzed post-mortem tissues from fetuses with severe CDH (n = 7). Histology and immunohistochemical distribution of desmin, muscle actin [HHF35], endothelin-1 [ET-1] and TGF-β were evaluated. Results In the atrium, desmin, HHF35, ET-1, TGF-β were found expressed only in preterm CDH. Dishomogeneous ventricular distribution of cardiac growth factors were detected in term CDH. The cardiomyocyte nucleus/cytoplasmatic ratio in CDH was higher compared with controls (p = 0.01). Small intramyocardial artery density and vascular wall thickness was increased in CDH compared with controls (p = 0.03 and p < 0.01). In comparison with the ventricles, the interventricular septum showed a greater vessel density (p = 0.01) and a greater vascular wall thickness, particularly compared with the CDH right ventricle (p = 0.02). Conclusion Left ventricle immaturity seems to be a cardiac adaptive response of severe CDH in utero.