In 11 neonates of diabetic mothers echocardiography was systematically performed and led to the discovery of 6 cases with hypertrophic cardiomyopathy. This abnormality, which may induce cardiorespiratory failure, is usually benign and consists of systolic murmur and transitory cardiomegaly; all these symptoms spontaneously regress within a few weeks. This cardiomyopathy may present with obstructive signs requiring treatment with beta adrenergic blocking agents; however, it is more often pure and needs no treatment. It may be observed after pregnancies that were not well supervised and might be induced by fetal hyperinsulinism.