A new study has uncovered crucial insights into the impact of chronic endometritis (CE) and endometrial dysbiosis (ED) on infertility, particularly in cases of recurrent implantation failure (RIF). RIF, which refers to the repeated inability to achieve pregnancy despite transferring high-quality embryos, is one of the most significant obstacles in fertility treatments. Recent research at the University of Tokyo has revealed that chronic endometritis and endometrial dysbiosis may play a critical role in these fertility challenges.
Chronic Endometritis and Endometrial Dysbiosis: A Hidden Barrier to Pregnancy
CE, which can be diagnosed via hysteroscopy or the endometrial CD138 test, has been identified in 30-57% of RIF patients. Meanwhile, endometrial dysbiosis—a condition marked by disruptions in the endometrial microbiome, particularly the reduction of Lactobacillus bacteria—has emerged as another key contributor to implantation failure. Understanding the relationship between CE, ED, and their influence on embryo implantation is vital for developing effective treatments to improve pregnancy outcomes.
A comprehensive study conducted between April 2019 and March 2024 at the University of Tokyo Hospital examined the prevalence and treatment efficacy of CE and ED in 73 RIF patients. The results revealed that CE was diagnosed in 56.2% of patients via hysteroscopy and 49.3% by the CD138 test. Meanwhile, ED was identified in 53.4% of patients, making it a prominent factor in implantation failure.
Impact of Endometrial Dysbiosis on Pregnancy Success
One of the most striking findings of the study was the significant improvement in pregnancy outcomes for patients diagnosed with ED. Among those who received treatment for ED, 88.9% achieved clinical pregnancy—markedly higher than the 56.0% pregnancy rate in patients without ED (p = 0.021). The odds ratio (OR: 6.29, p = 0.031) further confirmed the strong association between ED and successful pregnancy outcomes, underscoring the importance of testing the endometrial microbiome as part of fertility assessments.
Patients diagnosed with ED underwent a treatment regimen that included antibiotics and vaginal Lactobacillus probiotics to restore a healthy microbiome. After a two-week treatment course, probiotics were continued to support the endometrial environment. The study showed that 69.8% of patients achieved clinical pregnancy, with the highest success rates observed among those treated with both antibiotics and Lactobacillus, showing a pregnancy rate of 88.9% compared to 60% for those receiving antibiotics alone (p = 0.045).
The Need for Personalized Approaches in Fertility Testing
Despite these promising findings, the study revealed that there were no correlations between CE diagnoses via hysteroscopy, CD138 test, and ED, suggesting that these tests may not always capture the same patient population. The researchers noted that the tests may be identifying different underlying conditions affecting fertility, which emphasizes the need for individualized patient assessments. The absence of overlap between test results reinforces the need for incorporating endometrial microbiome testing into routine evaluations for RIF patients to better understand and treat underlying causes of infertility.
Future Directions and Implications for Reproductive Health
The study calls for further prospective research to validate the link between ED treatment and improved fertility outcomes, particularly in diverse populations beyond the Japanese cohort studied. The authors stress the importance of re-testing protocols for CE and ED patients after treatment, which could provide more insights into the effectiveness of these interventions and their impact on long-term fertility.
This groundbreaking research highlights the potential of addressing chronic endometritis and endometrial dysbiosis to significantly improve reproductive outcomes for couples struggling with recurrent implantation failure. By focusing on the health of the endometrium and leveraging microbial treatments, fertility specialists may be able to enhance current approaches to infertility treatment, potentially transforming the management of RIF and increasing success rates in assisted reproductive technologies.
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