The authors report a case of isolated double orifice mitral valve in a 20-year old pregnant woman. This exceptional and seldom isolated anomaly is usually discovered at autopsy or surgery. In this particular case it was diagnosed by pulsed doppler ultrasound combined with echocardiography. Data from the literature are reviewed on that occasion, and the echocardiographic images of the malformation are described. Despite its rarity, double orifice mitral valve deserves to be known and its presence should be looked for by echocardiography, notably in patients with complete or partial atrioventricular canal.