This research significantly contributes to the public health sector, particularly within fetal cardiology and prenatal care. By assessing the reliability of fetal cardiac strain measurements, this thesis evaluates whether Speckle Tracking Echocardiography (STE) can be reliably implemented into routine clinical practice. Currently, STE is not used in prenatal clinical practice due to missing reference intervals and uncertainty surrounding its reliability. Demonstrating high reliability can support the creation of standardized reference ranges, facilitating clinical adoption. Clinicians, including obstetricians, cardiologists, and sonographers, will especially benefit, as STE offers distinct advantages over traditional methods. It is easier to interpret, less dependent on the angle of insonation compared to the currently used method (Doppler), potentially improving clinical confidence in diagnosing and managing fetal heart conditions. From a broader societal perspective, establishing reliable STE measurements can refine prenatal care guidelines, influence public health policies, and ultimately enhance maternal- fetal health. These findings could stimulate further research and technological innovation, thereby advancing ultrasound capabilities and prenatal medical practice.