Congenital aneurysm of the left ventricle is a rare condition of unknown origin, the main differential diagnosis of which is the diverticulum. The natural history of this pathology is well known in adults and adolescents, contrary to those forms diagnosed by foetal echocardiography. Based on a case of congenital left ventricular aneurysm diagnosed ante-natally and a review of the literature, the authors propose echocardiographic prognostic factors useful for prenatal management. Thus, early antenatal diagnosis, size and progression of the aneurysm, signs of antenatal cardiac failure, are poor prognostic factors and should be discussed during parent counselling.