The microbiota at the female reproductive tract in successful IVF-ET and RIF

Repeated implantation failure (RIF) is a critical problem which imperils the success of in vitro fertilization and embryo transfer (IVF-ET), but its causes remain unclear. Microorganisms residing the upper genital tract have emerged as possible contributors to RIF. Here we characterized the microbiota at three sites of the reproductive tract in women with successful IVF-ET and those with RIF. 16S rRNA sequencing revealed pronounced difference in the composition of microbiota at the genital tract between these two groups. The cervico-uterine microbiota of RIF patients was featured by reduced diversity and depletion of numerous signature taxa across the reproductive tract. This compositional shift was coupled with alterations in a wide spectrum of microbial functions, especially in multiple pathways of nutrient metabolism. Altogether, our study provided evidence for the link between genital microbiome and outcome of IVF-ET.