Differential Composition of Vaginal Microbiome, but Not of Seminal Microbiome, Is Associated With Successful Intrauterine Insemination in Couples With Idiopathic Infertility: A Prospective Observational Study

Abstract

Background Vaginal and seminal microbiomes have gained increasing interest for their involvement in reproductive health and fertility. However, their role in reproductive outcome is not fully understood yet. In this study, we aimed to correlate the vaginal and the seminal microbiome of 23 couples with idiopathic infertility to the clinical pregnancy rate after intrauterine insemination (IUI). Methods Vaginal swabs and seminal fluids were collected on the day of IUI procedure and analyzed through polymerase chain reaction amplification of variable regions 3 and 4 (V3–V4) of 16S ribosomal ribonucleic acid genes and Illumina MiSeq sequencing. The taxonomic data were then correlated to IUI success. Results Idiopathic infertile women showed a different average composition of vaginal microbiome compared with control sequences, whereas for seminal counterpart no relevant differences were observed. Furthermore, among idiopathic infertile women, different patterns of Lactobacillus species dominations were observed, with a predominance either of Lactobacillus crispatus, a marker of a healthy vaginal ecosystem, or of Lactobacillus iners and Lactobacillus gasseri, associated with a more dysbiosis-prone environment. More important, considering all investigated variables, vaginal L crispatus domination was the only factor strongly associated to IUI success (P = .0002). Conclusions Our results strengthen the potential role of L crispatus in promoting a favorable environment for pregnancy and suggest that microbiome characterization could be useful, together with standard clinical and laboratory assessments, in the pre-IUI evaluation of infertile couples.

Microbiota and Human Reproduction: The Case of Female Infertility

“…Interestingly, they found that the prevalence of Gardnerella vaginalis in the vaginal microbiome was higher in women whose partners had leukocytospermia; in addition, they also highlighted a reduction of Lactobacillus crispatus and a high concordance between semen and vaginal microbiome, after sexual intercourse [ 99 ]. Subsequently, Amato et al analyzed the vaginal and seminal microbiome of 23 couples with idiopathic infertility with the aim to correlate microbial features with the pregnancy rate after intrauterine insemination [ 100 ]. They found that the vaginal microbiome of idiopathic infertile women differed from controls, whereas the semen not; in addition, they found, among the vaginal microbiome of idiopathic infertile women different patterns of Lactobacillus species, Lactobacillus crispatus being associated to the higher rate of intrauterine insemination success [ 96 ].…”

The Impact of Female Genital Microbiota on Fertility and Assisted Reproductive Treatments

“…In respect of the vagina, Campisciano et al found that infertile patients (especially those with idiopathic infertility) had higher richness and diversity of species than healthy controls (Chao1: Control – 419, Idiopathic – 579 - p<,05; Simpson’s index: Control - 1,5, Idiopathic – 2,4, Infertile – 2,6 – p<,05) ( 40 ). In contrast, Amato et al found no statistically significant differences in diversity between infertile patients and controls ( 41 ). Likewise, Kitaya et al found no differences in diversity between patients with history of RIF showed compared to other infertile patients ( 35 ).…”

“…flora in disfavour of L. iners and L. crispatus that may be a cause for some of the idiopathic infertility, rather than isolated bacteria dominance ( 40 ). Amato et al found a similar trend but with no statistical significance, maybe due to the small size of the sample ( 41 ).…”

“…No differences were found in Bifidobacterium spp. composition of VM between infertile and healthy patients ( 41 ).…”

“…Amato et al reported lower diversity in VM in patients who achieved pregnancy after IUI (mean SDI of 1,5 in pregnant group and 0,8 in non-pregnant group p=,003) ( 41 ). Likewise, Haahr et al found that a Shannon index higher than 0,93 in VM was associated with less clinical pregnancy and LBR after IVF (odds ratio of pregnancy = 0,1 - p=,01) ( 43 ).…”