Human gut microbiota contains around 1014 colonized intestinal microbes.Gut microbiome outnumbers the human gene pool by ten to one.Therefore,it's generally considered to be our "second gene pool".Several research have clarified that the cycle of "maternal intestinal microbes-placental microbes-fetal intestinal microbes" plays a critical role in the neurological and immune regulation and metabolism in infants,which may contribute to the furtherance of research on gut microbes.We summarized the factors affecting the colonization of maternal and fetal gut microorganisms during perinatal period from recent research.