Introduction: Do microbes in the female reproductive function matter?

For more than a century, the uterine cavity has been considered a sterile site maintained by the cervical plug. Humans are like coral that need symbiosis with microorganisms to be completely functional. In the era of precision medicine, the endometrial factor and specifically the microbiological view have long been neglected in reproduction, because it was considered an old concept with no potential improvement. In the last decade, important discoveries, led by improving technology, namely next generation sequencing, have been made in the study of microbial communities not only in the vagina but also in the endometrial cavity and its implication in reproductive health and disease, particularly chronic endometritis. From these studies, we have learned that microbes interact with the host cells along the female reproductive tract generating the physical, chemical and biological environment that the embryo will encounter during the peri-implantation period and throughout pregnancy.