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

Objective To evaluate the impact of vaginal microbiota on pregnancy outcomes in women undergoing assisted reproduction. Design A prospective cohort study. Setting A university-based assisted reproductive technology (ART) centre. Population 223 women undergoing ART treatment. Methods 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. Main outcome measures ART clinical outcomes (implantation, clinical pregnancy rates and live birth rates). Results 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. Conclusions Streptococcus has the highest contribution to the distinction between the PR and NP groups. Tweetable abstract A relatively high abundance of Streptococcus in the vaginal microbiota may be associated with a lower ART success rate.