#271 : Association Between Monoaromatic Hydro Exposure and Vaginal Microbiota Disorder in Recurrent Implantation Failure

Background and aims: MACHs are present in common everyday products and are defined as endocrine disrupting chemicals (EDCs) that can negatively impact human health by interfering with the endocrine system. There is a lack of human studies on the association between MACHs and the microbiota in the female reproductive tract. In this study, we recruited a prospective randomized controlled cohort to investigate potential correlations between MACHs exposure and the vaginal microbiota, as well as their potential impacts on embryo implantation. Methods: This study recruited a randomized controlled cohort prospectively to investigate the correlation between MACHs exposure and the vaginal microbiota, as well as their potential impact on embryo implantation. The types and concentrations of MACHs exposure were detected using LC-MS, while the vaginal microbiota was characterized by metagenomics. Results: The findings reveal that exposure to MEHP, Methyl N-methylanthranilate, and Benzene was associated with a disruption of the microbial community structure in the recurrent implantation failure (RIF). The RIF group exhibited an instable vaginal microbial community structure, with reduced abundance of Lactobacillus spp. and increased abundance of potentially pathogenic bacteria, such as Streptococcus anginosus, Peptoniphilus asaccharolyticus. The atypical composition of the vaginal microbiota was associated with unfavorable pregnancy outcomes. Impairment of sphingolipid metabolism was a crucial factor for abnormal microbiota to trigger unfavorable pregnancy outcomes. Furthermore, exposure to Methyl N-methylanthranilate and MEHP was associated with reduced abundance of Lactobacillus spp. (including L.crispatus and L.jensenii) and reduction of the protective barrier function of the reproductive tract. Conclusions: Multiple MACHs, such as Benzene, Methyl N-methylanthranilate, and MEHP, were associated with changes in the RIF group’s vaginal microbiota. MACHs exposure might cause embryo implantation failure by affecting the vaginal microbial composition.