The main types of atrial septal defects (ASD), ventricular septal defects (VSD) and atrioventricular septal defects (AVSD) are described in this chapter focusing on the tools to performing prenatal diagnosis using three-dimensional (3D) ultrasound. Abnormalities of foramen oval (restrictive foramen ovale and aneurysm of membrane), images of a variety of septal defects with schematic drawing are presenting to aide an easier comprehension of the fetal 3D views and fourdimensional (4D) navigation. Associated aneuploidies, genetic syndromes and other structural malformations (cardiac and extracardiac) are also presented. Indeed, virtual navigation are included in this section since this advanced technology can be used as interesting additional diagnostic tools to the current standard imaging armamentarium, enabling us to improve the quality of prenatal parental counseling and to optimize of cardiac surgical planning.