The trend in the development of ventricular ostium was traced in fetuses at 14-15 to 41-42 weeks gestation via the continuous sampling method, by examining a lot of observations. The authors established the specific features of fetal blood circulation: the increased diameter of efferent great vessels and ostia corresponding to the location of the tricuspid valve and pulmonary artery. It is recommended to use the morphometric parameters of the heart and great vessels in autopsy practice for the objective assessment of cardiogenesis.