Embryonic diapause is a survival strategy and reproductive state that is widespread in mammals. It starts priorto implantation when embryo development is minimized or put on hold, and terminates when embryo development is reactivated.Embryonic diapause is supposed to be reversible and harmless to the subsequent embryo development and it
has two types: facultative diapause and obligate diapause. Facultative diapause is activated by lactation whereas obligate diapause is activated by seasonal photoperiod. The entrance, maintenance, and reactivation of embryonic diapause are all regulated by the relative levels of prolactin, progesterone, or ovarian estrogen. In addition to hormone regulation, the molecular mechanisms of embryonic diapause have been studied in several mammal species. A large number of potential factors that could regulate embryonic diapause were reported, including nutrients, proteases, cytokines, growth factors and transcription factors. In the present study, we reviewed previous studies on embryonic diapause, summarized current knowledge, and then proposed some scientific suggestions for further research needed on this topic.