We report a rare case of a newborn with complete monosomy 21 prenatally diagnosed in the amniotic fluid and subsequently confirmed in other tissues. Patient presented with multiple osseous, cardiac, and vascular anomalies. Cardiac anomalies included large atrial septal defect, ventricular septal defect, aneurysm of the left pulmonary artery and patent ductus arteriosus with large bidirectional shunt. Interruption of the inferior vena cava was noted. Although interrupted inferior vena cava associated with cardiac anomalies was previously reported, it has not been reported in association with monosomy 21.