ObjectiveThe role ofLactobacillus-dominant microbiota in the
endometrium in reproductive function is unclear. We therefore aimed to
explore the impact of the balance ofLactobacillusand
pathological bacteria in the endometrial and vaginal microbiomes on the
pregnancy outcomes of women treated with assisted reproductive technology
(ART).MethodsThis study included 35 women with infertility submitted to good-quality
embryo transfers. The cutoff values for abundance ofLactobacillusspecies (spp.) and pathological bacteria
in the endometrium and vagina were calculated. Women withLactobacillusspp. and pathological bacteria abundance
above the cutoff values were categorized in the high-abundance group,
whereas those with abundance below cutoff values were categorized in the low
abundance group. We divided the patients into four groups based on the
combination of high/low abundance ofLactobacillusspp. and
pathological bacteria.ResultsThe 35 cases of good-quality embryo transfer resulted in 21 pregnancies.
Pregnant women were present in significantly higher proportions in the highLactobacillusspp. abundance and low pathological
bacteria abundance group, whereas the opposite combination (i.e., lowLactobacillusspp. abundance and high pathological
bacteria abundance) saw a significantly higher proportion of nonpregnant
women (p=0.022).ConclusionsThe balance betweenLactobacillusand pathological bacterial
abundance in the endometrial and vaginal microbiomes is associated with
pregnancy from ART.