The Role of the Physiological Endometrial Microbiota in Assisted Reproduction Outcomes

NCT07606053 | Enrolling By Invitation DMC

• 2 other identifiers: Microbiome-AN011Assisting Nature
• Study Type: observational
• Target: 80
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this observational study is to investigate the influence and contribution of the normal composition and balance of the endometrial microbiota on the achievement of embryo implantation and the maintenance of pregnancy in women undergoing IVF, with comparable clinical profiles, including patients with a history of RIF or RPL, evaluated under identical treatment protocols and hormonal conditions. The main questions it aims to answer are:

1. 1.Does the normal composition of the endometrial microbiota, particularly the dominance of Lactobacillus species, influence embryo implantation success in women undergoing IVF?
2. 2.Does the endometrial microbiota profile affect pregnancy maintenance, ongoing pregnancies, and live birth rates in women with a history of recurrent implantation failure (RIF) or recurrent pregnancy loss (RPL)

Conditions

Repeated IVF Failure; Microbiota

Keywords

Physiological Endometrial Microbiota; Endometrial Microbiota; IVF; In vitro fertilization; Assisted reproduction; Implantation success; Embryo; Endometrial Microbiome; Microbiota; Microbiome

Outcome Measures

Primary Outcomes (3)

• Implantation Rate according to microbiome profile

  The study formally assesses differences in embryo implantation rates between women with Lactobacillus-dominant and non-Lactobacillus-dominant endometrial microbiota profiles.

  From the day of the embryo transfer to the day of confirmation of implantation (2-4 weeks)

• Ongoing Pregnancy/Live Birth Rate according to microbiome profile

  Association between endometrial microbiota composition and the likelihood of achieving an ongoing pregnancy or live birth

  From the day of embryo transfer up to the end of the first trimester (up to 12 weeks of gestation) and live birth until delivery (up to 40 weeks of gestation)

• Biochemical pregnancy rate and microbiome status

  Rate of biochemical pregnancies in relation to endometrial microbiota profile

  From the day of embryo transfer to the day of confirmation of implantation (2-4 weeks)

Secondary Outcomes (1)

• Endometrial microbiota composition

  At time of biopsy collection (during procedure)

Study Arms (2)

Lactobacillus-dominant microbiota

Participants whose endometrial microbiota is dominated by Lactobacillus species. Data were collected from previously obtained endometrial biopsies, analyzed via 16S rRNA gene sequencing. No interventions were performed beyond standard IVF clinical care.

Non-Lactobacillus-dominant microbiota

Participants whose endometrial microbiota shows depletion of Lactobacillus species or presence of potentially pathogenic microorganisms. Data were collected from previously obtained endometrial biopsies, analyzed via 16S rRNA gene sequencing. In some cases, participants received individualized clinical interventions (e.g., antibiotics or probiotics) based on their microbial profile as part of routine care.

Eligibility Criteria

• Age: 18 Years - 54 Years
• Gender Eligibility Details: Participation is limited to individuals with female biological sex, due to the requirement for endometrial tissue sampling and pregnancy-related outcomes.
• Healthy Volunteers: No
• Age Groups: Adult (18-64)
• Sampling Method: Non-Probability Sample

Study Population

Participants were required to be between 18 and 54 years of age, in accordance with the legally permitted age limits for embryo transfer in Greece

You may qualify if:

• Individuals who are biologically female.
• Age between 18 and 54 years, in accordance with the legally permitted age limits for embryo transfer in Greece.
• Undergoing in vitro fertilization (IVF) treatment.
• Clinical history consistent with recurrent implantation failure (RIF) or recurrent pregnancy loss (RPL) and comparable IVF treatment profiles.
• Ability to provide informed consent for the use of clinical and microbiome data for research purposes

You may not qualify if:

• Individuals who are not biologically female.
• Age below 18 or above 54 years.
• Absence of endometrial biopsy samples or incomplete clinical data.
• Presence of significant uterine abnormalities or medical conditions that contraindicate embryo transfer.
• Participation in another interventional clinical study that may interfere with microbiome assessment or IVF outcomes.

Sponsors & Collaborators

• Assisting Nature: lead

Study Sites (1)

Assisting Nature

Thessaloniki, Greece

Location

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Target Duration: 3 Months
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: February 20, 2026
• First Posted: May 26, 2026
• Study Start: January 2, 2025
• Primary Completion: May 30, 2026
• Study Completion: June 25, 2026
• Last Updated: May 26, 2026

Record last verified: 2026-05

Locations

GR (1)