The vaginal microbiota composition of women undergoing assisted reproduction: a prospective cohort study.

<bold>Objective: </bold>To evaluate the impact of vaginal microbiota on pregnancy outcomes in women undergoing assisted reproduction.<bold>Design: </bold>A prospective cohort study.<bold>Setting: </bold>A university-based assisted reproductive technology (ART) centre.<bold>Population: </bold>223 women undergoing ART treatment.<bold>Methods: </bold>Prior to embryo transfer, vaginal samples were collected from the posterior fornix. Vaginal microbiota identification was carried out using next-generation sequencing and categorised according to the V3-V4 hypervariable region in the 16S rRNA gene region.<bold>Main Outcome Measures: </bold>ART clinical outcomes (implantation, clinical pregnancy rates and live birth rates).<bold>Results: </bold>The live birth rate in women with community state type (CST)-I (39%) was higher than that in women with CST-III (21.5%) but the difference was not statistically significant (P = 0.052). The relative abundance of Lactobacillus was lower in women who failed to become pregnant (NP group) (67.71%) than in women who became pregnant (PR group) (79.72%). However, this difference was not statistically significant (P = 0.06). In the NP group, the relative abundance of Streptococcus (7.81%) and Gardnerella (9.40%) was higher than that in the PR group (relative abundance of Streptococcus and Gardnerella was 2.28% and 5.56%, respectively). The abundance of Streptococcus was found to be statistically significantly different between the two study groups (P = 0.014). Linear discriminant analysis (LDA) further validated that Streptococcus had the highest contribution (LDA score >4.0) to the difference between these two groups.<bold>Conclusions: </bold>Streptococcus has the highest contribution to the distinction between the PR and NP groups.<bold>Tweetable Abstract: </bold>A relatively high abundance of Streptococcus in the vaginal microbiota may be associated with a lower ART success rate. [ABSTRACT FROM AUTHOR]