Endometrial microbiota composition is associated with reproductive outcome in infertile patients Original paper

What was studied?

This study investigated the association between endometrial microbiota composition and reproductive outcomes in infertile patients undergoing assisted reproductive technologies (ART), including in vitro fertilization (IVF). Researchers specifically aimed to determine whether the presence or absence of specific bacterial taxa in the endometrial microbiota was linked to reproductive success, defined by live birth (LB), biochemical pregnancy (BP), clinical miscarriage (CM), or no pregnancy (NP). The study employed 16S rRNA sequencing to analyze both endometrial fluid and biopsy samples collected prior to embryo transfer.

Who was studied?

The study included 342 infertile women, aged 21 to 49, from 13 reproductive clinics across Europe, America, and Asia. These women were undergoing IVF or ovum donation treatments and had an average age of 36 years. The cohort consisted of patients with a variety of infertility causes, including advanced maternal age, male factor infertility, unexplained infertility, and ovarian pathology. All participants underwent a hormone replacement therapy cycle before embryo transfer, and their endometrial microbiota composition was analyzed to correlate it with reproductive outcomes.

What were the most important findings?

The study found significant differences in the endometrial microbiota composition between patients with successful reproductive outcomes (live birth) and those with unsuccessful outcomes (biochemical pregnancy, clinical miscarriage, or no pregnancy). Lactobacillus spp., particularly dominant in the endometrial microbiota, was consistently enriched in women who achieved live birth. In contrast, patients with unsuccessful outcomes exhibited a dysbiotic microbiota profile, characterized by higher levels of potentially pathogenic bacteria, including Gardnerella, Haemophilus, Klebsiella, Neisseria, Streptococcus, and Atopobium. These dysbiotic profiles were strongly associated with lower pregnancy rates and higher miscarriage rates. The study found that the microbiota composition of endometrial fluid (EF) and endometrial biopsy (EB) samples showed some discrepancies, though both sample types revealed similar associations with reproductive outcomes. The presence of Lactobacillus spp. was inversely correlated with pathogenic bacteria in successful pregnancies, highlighting its potential role in preventing microbial dysbiosis and ensuring a healthy reproductive environment conducive to embryo implantation.

What are the greatest implications of this study?

The study’s findings emphasize the importance of endometrial microbiota composition as a predictive biomarker for reproductive outcomes in infertility treatments. Clinicians can use this information to assess the microbial health of the endometrium before embryo transfer and potentially identify candidates who may benefit from interventions aimed at restoring a healthy microbiota. This may involve the use of probiotics, antimicrobial therapies, or other microbiome-modulating strategies to enhance the likelihood of a successful pregnancy, particularly in cases of recurrent implantation failure or unexplained infertility. Additionally, the results support the need for further research into the mechanisms by which specific pathogens disrupt implantation and pregnancy, potentially leading to improved diagnostic and treatment protocols for ART patients.