Characterization of the Vaginal Microbiome in Women with Infertility and Its Potential Correlation with Hormone Stimulation during In Vitro Fertilization Surgery Original paper

What was studied?

This study investigated the composition and diversity of the vaginal microbiome in women experiencing secondary infertility who were undergoing in vitro fertilization and embryo transfer (IVF-ET). The researchers compared the vaginal microbiota of 30 women with secondary infertility to that of 92 healthy, reproductive-age women. They also evaluated whether hormone stimulation during IVF affected the vaginal microbiome in these infertile patients. By analyzing vaginal swab samples using 16S rRNA gene sequencing, the study aimed to clarify how the microbiome’s structure changes in infertile women, its sensitivity to hormonal manipulation, and the potential implications for IVF outcomes.

Who was studied?

The study included 30 Chinese women aged 23–42 years diagnosed with secondary infertility and scheduled for IVF-ET, alongside 92 age-matched healthy women with no history of infertility or reproductive complications. All participants were HIV negative, had regular menstrual cycles, and had not received significant treatments within four weeks prior to enrollment. Vaginal swabs from infertile women were collected both before ovulation induction and after hormone stimulation. Healthy controls provided samples during both the follicular phase and the ovulation period, allowing for assessment of natural cyclic changes versus those observed in infertile women during IVF.

What were the most important findings?

The study revealed that women with secondary infertility exhibited significantly reduced vaginal microbiome diversity and richness compared to healthy controls during the follicular phase. The vaginal microbiome of infertile women was notably less dynamic than that of healthy women, who displayed substantial microbial fluctuations during ovulation. Infertile women demonstrated a persistent alteration in their microbiome, with increased abundance of genera such as Atopobium, Aerococcus, and Bifidobacterium, and a decreased presence of protective genera like Lactobacillus and Leuconostoc. In contrast, healthy women experienced predictable microbiome shifts with hormonal changes, particularly an increase in beneficial bacteria during ovulation. Importantly, hormone stimulation with GnRH agonist and r-hCG during IVF had no significant effect on the vaginal microbiome of infertile women, indicating a form of hormone insensitivity. Further correlation analysis suggested that the altered microbiome in infertile patients involves synergistic dysbiotic interactions between various anaerobic bacteria, such as Atopobium, Prevotella, Bifidobacterium, and Megasphaera.

What are the greatest implications of this study?

This study strongly suggests that a stable, hormone-responsive vaginal microbiome is critical for female reproductive health and successful IVF outcomes. The finding that infertile women’s vaginal microbiota remain dysbiotic and largely unresponsive to hormonal stimulation points to an underlying microbiological barrier to fertility that current IVF protocols may not address. For clinicians, these results highlight the importance of evaluating and potentially modifying the vaginal microbiome in women undergoing IVF, particularly those with a history of secondary infertility. Personalized interventions, such as microbiome modulation through probiotics or targeted antimicrobials, could enhance the effectiveness of ART by restoring a healthy, Lactobacillus-dominated microbiota and improving receptivity to hormonal treatments. This study also underscores the need for future large-scale research to refine microbiome-targeted diagnostics and therapies as adjuncts to conventional infertility treatments.