Vaginal and semen microbiota parameters in 475 infertile couples undergoing IVF

Photo by National Institute of Allergy and Infectious Diseases / Unsplash

Frontiers in Medicine Published April 29, 2026 Medically reviewed April 29, 2026 DOI ↗ By Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

Key Takeaway

Note that positive microbiota cultures are common in infertile couples undergoing IVF.

This retrospective cohort study examined baseline clinical, biochemical, and microbiological parameters in a population of 475 infertile couples undergoing IVF with or without intracytoplasmic sperm injection at the University of Szeged. The setting was a single institution, and the study phase was not reported. Funding or conflicts of interest were not reported.

Positive vaginal cultures were identified in 121 women, representing 25.5% of the sample. The most common pathogens in these positive cultures were Candida albicans (26%), Streptococcus agalactiae (17%), and Escherichia coli (17%). Positive semen cultures were identified in 134 men, representing 29% of the sample. The most common pathogens in these positive semen cultures were Enterococcus faecalis (46%) and Escherichia coli (23%).

Pathogen overlap between partners was rare, observed in 13 couples. The study did not report clinical pregnancy outcomes, safety data, adverse events, or tolerability. Consequently, the relationship between microbiota findings and pregnancy rates remains unclear based on this data.

Study Details

Study typeCohort

EvidenceLevel 3

PublishedApr 2026

View Original Abstract ↓

IntroductionInfertility affects 15–20% of couples, with 3% of Hungarian children conceived through in vitro fertilization (IVF). Predicting IVF outcomes before treatment initiation remains challenging. Emerging evidence suggests that the vaginal and seminal microbiota influence reproductive health by modulating local immunity, implantation, and gamete function. This study aimed to evaluate associations between baseline clinical, biochemical, and microbiological parameters and IVF outcomes.Material and methodsWe conducted a retrospective, single-center cohort study including 475 couples undergoing IVF with or without intracytoplasmic sperm injection at the University of Szeged (January 2022–December 2023). Data collection encompassed maternal demographics, reproductive history, baseline hormone levels, ovarian stimulation characteristics, and endometrial thickness. The results of microbiological cultures of vaginal discharge and semen samples, including Lactobacillus colonization, pathogen distribution, and the antibiotic resistance status of the pathogens, were recorded. The primary outcome was clinical pregnancy. Machine learning models, including support vector machine (SVM), random forest (RF), and extreme gradient boosting (XGBoost) were applied, to explore the predictive value of combined clinical and microbial features for IVF outcome.ResultsPositive vaginal cultures were identified in 121 women (25.5%), most commonly Candida albicans (26%), Streptococcus agalactiae (17%), and Escherichia coli (17%) among the positive cases. Among 134 men (29%) with positive semen cultures, Enterococcus faecalis (46%) and Escherichia coli (23%) predominated. Single-organism growth predominated, and pathogen overlap between partners was rare (13 couples,