Mitral valve dysplasia syndrome (MVDS) is a rare and severe form of left-sided congenital heart disease (CHD). Prenatal distinction from isolated aortic stenosis and hypoplastic left heart syndrome (HLHS) is critical for postnatal management. We present the sonographic markers of MVDS through a case. A 29-year-old primigravida was referred to us for a mid-trimester scan. Her previous history was unremarkable. A level II ultrasonography with detailed cardiac evaluation was performed as per ISUOG guidelines. Cardiac examination revealed an abnormal four chamber heart with left atrial and ventricular dilatation. The left ventricular wall was echo-bright with poor contractility suggestive of endocardial fibroelastosis. The mitral valve (MV) was thickened with evidence of regurgitation. The foramen ovale was highly restrictive. Aortic stenosis (AS) and an aortic arch of reduced calibre was seen. The three vessel view showed that aorta was smaller than pulmonary artery with reversal of flow in the aortic arch. The spectral Doppler of pulmonary veins showed the ‘double reversal’ sign. The family chose to continue with the pregnancy. A pediatric cardiologist opinion was sought and a postnatal plan was laid out. The patient delivered a 2750 gm male baby at term gestation. Balloon valvotomy was performed on day one itself however, the baby succumbed later. MVDS is a novel and critical anomaly of the left heart. The specific constellation of sonographic findings helps us in grading its severity and distinguishes it from isolated severe aortic stenosis and HLHS. Spectral Doppler of pulmonary vein helps in prognostication. A dilated left atrium with severe mitral regurgitation, thickened MV and restrictive foramen ovale suggest severe AS with MVDS, which has an extremely poor prognosis. Obstetric sonologists must be aware of this rare cardiac anomaly. Distinction from isolated critical aortic stenosis has treatment implication.