Energetic electron precipitation from the magnetosphere deposits energy into the ionosphere, changes ionosphere chemistry, affects ozone concentration, and causes aurora. This precipitation is primarily caused by interactions between energetic electrons and plasma waves. One of the most important wave types responsible for driving electron precipitation is whistler-mode waves. These waves can lead to periodic electron precipitation, which is associated with the formation of pulsating aurora. Periodic precipitation can also involve relativistic electrons, resulting in significant ionospheric responses. In this study, we statistically analyze the properties of periodic electron precipitation events. The main finding is that such periodic precipitation of relativistic electrons is frequently observed and is likely driven by the coupling of whistler-mode waves and ultra-low-frequency geomagnetic pulsations.