Impact of Lactobacillus in the uterine microbiota on in vitro fertilization outcomes.

Abundant intrauterine Lactobacillus is associated with good in vitro fertilization (IVF) outcomes; however, whether specific species of Lactobacillus have any benefit remains unclear. So we examine the effect of Lactobacillus on the clinical outcomes of IVF at the species level. Uterine microbiota were classified as either Lactobacillus -dominant (LD) or non- Lactobacillus -dominant. In the LD group, we further investigated the clinical results for each Lactobacillus species and evaluated them in relation to IVF outcomes. In Uterine microbiome analysis, Lactobacillus was the most abundant, with the four species of L. crispatus, L. iners, L. gasseri , and L. jensenii accounting for the great majority. We compared the clinical outcomes of single frozen-thawed embryo transfer conducted by Lactobacillus species and found that the implantation rate was lowest in those in whom L. iners was dominant. This study is the first to conduct a species-level analysis of the uterine microbiota and report on a detailed investigation of Lactobacillus , which was believed to be particularly helpful for pregnancy. • In Uterine microbiome, Lactobacillus formed the greatest proportion of all microbial species. • The four species of L. crispatus , L. iners , L. gasseri , and L. jensenii accounted for the majority. • Implantation rates were significantly lower in patients with predominant L. iners. • L. iners was more likely to coexist with Ureaplasma than other Lactobacillus spp. [ABSTRACT FROM AUTHOR]