The possibility of detecting acute hypoxic-ischemic brain lesions by prenatal magnetic resonance imaging or ultrasound is low. We present a case of a fetus with a vein of Galen arteriovenous malformation in whom prenatal diffusion-weighted magnetic resonance imaging at 33 weeks of gestation clearly detected cerebral acute ischemic lesions, associated with remarkable decrease of the average apparent diffusion coefficient, whereas T2-weighted imaging was still not informative.