{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T10:59:01Z","timestamp":1790852341357,"version":"4.1.0"},"reference-count":24,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T00:00:00Z","timestamp":1790812800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Clin. Med.","JCM"],"abstract":"<jats:p>Objective: We aim to assess gut and endometrial microbiota simultaneously in women with unexplained recurrent implantation failure (RIF) and explore the hypothesis of a gut\u2013endometrium microbial axis. Study design: This monocentric observational pilot study included women aged 38 years or younger with a history of RIF. Paired fecal and endometrial samples were collected on the same day and analyzed by 16S rRNA gene sequencing. Relative abundances of major phyla and alpha-diversity indices were compared between compartments. Results: Twenty-one women were included. Chronic endometritis was documented through hysteroscopy in all cases. Gut dysbiosis was observed in 20\/21 patients (95.2%), whereas endometrial dysbiosis was found in 16\/21 (76.2%); crude agreement between compartments was 71.4% (Gwet\u2019s AC1 0.62, 95% CI 0.25\u20130.90). The intestinal microbiota was dominated by Bacteroidetes (52.8% \u00b1 14.9%) and Firmicutes (33.3% \u00b1 11.0%), whereas the endometrial microbiota was enriched in Firmicutes (64.5% \u00b1 33.5%) and Proteobacteria (30.9% \u00b1 32.3%). Bacteroidetes were significantly more abundant in fecal than endometrial samples (p &lt; 0.001), while Firmicutes were significantly enriched in the endometrium (p = 0.001). All alpha-diversity indices were significantly higher in feces, indicating greater microbial richness and complexity in the gut. Conclusions: In this pilot cohort of women with unexplained RIF, gut and endometrial dysbiosis frequently co-occurred. These findings support a potential gut\u2013endometrium microbial axis and highlight the possible interplay between gut and endometrial microbiota in recurrent implantation failure. Further studies are warranted to better elucidate the clinical and biological implications of this relationship.<\/jats:p>","DOI":"10.3390\/jcm15197620","type":"journal-article","created":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T10:25:44Z","timestamp":1790850344000},"page":"7620","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Recurrent Implantation Failure and the Gut\u2013Endometrium Axis: A Pilot Study on Microbiota Crosstalk"],"prefix":"10.3390","volume":"15","author":[{"given":"Flora","family":"Caruso","sequence":"first","affiliation":[{"name":"Department of Public Health, School of Medicine, University of Naples \u201cFederico II\u201d, 80131 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-6911-301X","authenticated-orcid":false,"given":"Luigi","family":"Vigilante","sequence":"additional","affiliation":[{"name":"Department of Public Health, School of Medicine, University of Naples \u201cFederico II\u201d, 80131 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Danilo","family":"Borrelli","sequence":"additional","affiliation":[{"name":"Department of Public Health, School of Medicine, University of Naples \u201cFederico II\u201d, 80131 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9258-5883","authenticated-orcid":false,"given":"Alessandra","family":"Gallo","sequence":"additional","affiliation":[{"name":"Department of Public Health, School of Medicine, University of Naples \u201cFederico II\u201d, 80131 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"}]},{"given":"Ida","family":"Strina","sequence":"additional","affiliation":[{"name":"Department of Public Health, School of Medicine, University of Naples \u201cFederico II\u201d, 80131 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"validation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6485-5735","authenticated-orcid":false,"given":"Attilio","family":"Di Spiezio Sardo","sequence":"additional","affiliation":[{"name":"Department of Public Health, School of Medicine, University of Naples \u201cFederico II\u201d, 80131 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"validation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"}]},{"given":"Maria Rosaria","family":"Fantuz","sequence":"additional","affiliation":[{"name":"AMES Centro Polidiagnostico Strumentale, 80013 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-5274-3989","authenticated-orcid":false,"given":"Giovanni","family":"Savarese","sequence":"additional","affiliation":[{"name":"AMES Centro Polidiagnostico Strumentale, 80013 Naples, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"validation","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,10,1]]},"reference":[{"key":"ref_1","first-page":"623","article-title":"Infertility: Evaluation and Management","volume":"107","author":"Phillips","year":"2023","journal-title":"Am. 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