Right sinus venosus valve (RSVV) directs blood flow from inferior vena cava (IVC) to foramen ovale. Description of its anatomy related to fetal age can be important for the proper assessment of the heart on fetal autopsy. The study aimed to determine morphology of normally developed RSVV in the 1st and the 2nd trimester fetuses. Twenty normal fetal hearts aged from 10 to 23 weeks were submerged in water and dissected carefully to visualize the RSVV (figure). Nikon SMZ 1500 microscope, Nikon DS-Fi1 camera and NIS-Elements 3.00 software were used for observation and documentation. RSVV was present in all fetuses. Its inferior attachment was found between ostium of coronary sinus (CS) and the septal leaflet of tricuspid valve. In fetuses aged 10–15 weeks it covered the ostium of CS completely. The superior attachment was located in the region of sagittal bundle in fetuses younger than 20 weeks and in precaval segment of crista terminalis in older specimens. Starting from 16th week of gestation the division of RSVV into the valve of IVC and valve of CS was observed. In the fetuses aged 20 weeks and older the division of RSVV was distinct. The place of division was located in the region of Todaro’s tendon. Gradual regression of the RSVV was observed since 12th week of development. Conclusions: RSVV is constantly present in small fetal hearts. Its involution and division into IVC and CS valves can be observed. Further studies can help to determine the norm useful for pathologists.