This study investigates the effects of postbiotic intervention on vaginal microbiota in infertile patients. Using a pre-post test design, we will enroll 15 women aged 30-45 years with at least two IVF failures. Participants will receive postbiotic intervention for 8 weeks. Vaginal secretion samples will be collected before and after treatment for 16S rRNA sequencing analysis to assess microbial composition, dominant species distribution, α-diversity index, and Lactobacillus content. Primary outcomes include changes in vaginal microbiota composition and diversity, alterations in Lactobacillus abundance, and pregnancy rates in subsequent IVF-FET cycles.

Background The demand for infertility treatment is increasing, with approximately 10-15% of couples of reproductive age experiencing varying degrees of fertility issues. Vaginal microbiota dysbiosis may be a significant factor contributing to infertility, and a healthy vaginal microbiota environment plays a crucial role in embryo implantation. This study aims to investigate the effects of postbiotic intervention on the vaginal microbiota of infertile patients by analyzing the vaginal microbiota before and after bacteriocin treatment to evaluate its effectiveness in improving the vaginal microbial environment.

Objective This study aims to investigate changes in vaginal microbiota before and after the use of postbiotic intervention.

Methods This study employs a pre-post test design, planning to enroll 15 women aged 30-45 years diagnosed with infertility with at least two IVF treatment failure. All subjects must be free from severe gynecological diseases, not using antibiotics or probiotics, and without acute vaginal infection symptoms. The study period is 8 weeks. Before intervention, baseline data collection will include complete medical history and infertility treatment records. During the first visit, vaginal secretion samples will be collected for vaginal microbiota assessment through 16S rRNA sequencing analysis, simultaneously measuring Lactobacillus content and microbial diversity. Subjects will then use postbiotic intervention continuously for 8 weeks. After treatment, a second sampling will be conducted to re-analyze the vaginal microbiota. The primary outcome measures include changes in microbial composition before and after use, including dominant species distribution, α-diversity index, and changes in Lactobacillus content. All specimens will be collected, transported, and preserved following standard operating procedures to ensure testing quality. Research data will be analyzed using paired sample statistical methods to assess pre-post treatment differences, with significance level set at p<0.05.

Outcome

1. Compare differences in vaginal microbiota before and after using postbiotic intervention.
2. Compare differences in taxonomic abundance before and after using postbiotic intervention.
3. Check pregnancy rate of IVF-FET cycle after postbiotic intervention use

Inclusion Criteria:

• (1) age 30-45 years;
• (2) body mass index 18-30 kg/m²;
• (3) history of ≥2 prior IVF treatment failures despite transfer of good-quality embryos;
• (4) planned FET cycle;
• (5) willingness to comply with the eight-week postbiotic intervention protocol

Exclusion Criteria:

• (1) active acute vaginal infection with symptomatic presentation;
• (2) antibiotic or probiotic use within the preceding three months;
• (3) congenital uterine anomalies including septate, bicornuate, or unicornuate uterus;
• (4) severe intrauterine adhesions (Asherman syndrome grade III-IV);
• (5) history of gynecologic malignancy;
• (6) known allergy or hypersensitivity to Lactobacillus-derived products;
• (7) current ongoing pregnancy