Background: Three-dimensional fetal echocardiography is now a routine method of examination. Spatio-Temporal Image Correlation (STIC) modality allows to obtain four-dimensional reconstruction of the single fetal cardiac evolution basing on series of heart rate-gated images. The atrioventricular septum (AVS) is affected in numerous congenital cardiac malformations. Aim: Our study aimed to check whether STIC volume files can be used for morphometric analysis of the atrioventricular septum. Material and methods: Material for the study consisted of 50 STIC volume files acquired during routine echocardiographic examinations of fetuses aged 18-34 weeks of gestation using GE Voluson 730 Expert equipment. Files were processed offline using 4D-View software. Section Planes and Tomographic Ultrasound Imaging options were used for visualization and measurements. Hight, lenght and thickness of the AVS were measured basing on 5 parallel TUI images distributed equally throughout the lenght of the AVS. Results: TUI allowed for obtaining 5 parallel slices of AVS in three phases of the cardiac cycle – isovolumetric diastole, isovolumetric systole and when atrioventricular valves were completely open (Fig. 1). Quality of reconstructed images was satisfactory in all cases. Measurements were the easiest to perform in the middle of the AVS and in isovolumetric diastole. Measured values were repeatable in different section planes. Conclusions: We conclude that STIC four-dimenional echocardiography is a valuable method of assessment of visualization and morphometric analysis of normal fetal atrioventricular septum in vivo. It can be helpful to standardize methods of echocardiographic measurements.