Atrial, ventricular and atrioventricular septal defects are the most common cardiac anomalies in the humans and occur isolated or as part of other malformations in more than the half of children with a congenital cardiac anomaly. Whereas atrial defects are difficult to detect antenatally, ventricular and atrioventricular defects are detectable on two-dimensional and color Doppler ultrasound. Three-dimensional ultrasound as STIC technology allows in fetal septal defects on one hand a safe description and documentation of the finding and on the other hand a spatial demonstration of the defect with the possibility of getting new views into the heart. The choice of the ideal plane from a 3D volume enables to get the in-line visualization of the interventricular septum with the septal defect. Orthogonal views help to visualize the defect in the different planes. Tomographic imaging aids in getting the upper abdomen and the great vessels information in addition to the septal defect view, in order to rule out a complex malformation. Rendering mode with the enface view can be used to visualize the septum from a lateral view and the common atrioventricular valve in atrioventricular septal defects. The combination with color Doppler helps to get the spatial demonstration of the defect within the heart and provide in addition information on flow events during the cardiac cycle in septal defects.