Chronic endometritis (CE) is a long-lasting inflammation of the lining of the uterus. Many women with CE do not have symptoms, but the condition may affect fertility, embryo implantation, and pregnancy outcomes. CE is usually diagnosed during hysteroscopy, a procedure that allows doctors to look inside the uterus and collect a small tissue sample for laboratory testing.

The goal of this prospective cohort study is to learn how common CE is in women with infertility and to determine whether antibiotic treatment improves reproductive outcomes. The study will also examine whether hysteroscopic findings match laboratory-confirmed CE and whether certain findings can help doctors diagnose CE more accurately. In addition, researchers will study the types of bacteria found in the uterine lining and their possible relationship to fertility and pregnancy outcomes.

The main questions the study aims to answer are:

• How common is chronic endometritis in women undergoing infertility evaluation?
• Does antibiotic treatment improve fertility and pregnancy outcomes in women with CE?
• Can hysteroscopic findings reliably predict CE confirmed by laboratory testing?
• Are specific bacteria associated with poorer reproductive outcomes? Researchers will enroll approximately 100 women aged 18 to 40 years with diagnosed infertility who are scheduled for hysteroscopy and endometrial biopsy as part of infertility evaluation. Participants with severe systemic disease, pregnancy, inability to undergo hysteroscopy or antibiotic treatment, or allergy to study antibiotics without a suitable alternative will not be included.

Participants will:

• Undergo diagnostic hysteroscopy and endometrial biopsy
• Have tissue samples examined using histopathology and immunohistochemistry to identify CE
• Receive standardized antibiotic treatment if CE is confirmed
• Be followed for up to 12 months after treatment to monitor fertility outcomes
• Continue follow-up during pregnancy, if pregnancy occurs, to assess pregnancy and delivery outcomes Researchers will evaluate spontaneous pregnancies, embryo transfer success, implantation rates, miscarriage rates, time to pregnancy, and live birth outcomes. Pregnancy complications such as preeclampsia, placental disorders, premature rupture of membranes, and preterm birth will also be recorded.

The study is expected to run from January 2026 through December 2029. Data collected during the study may help improve the diagnosis and treatment of chronic endometritis in women with infertility and may support better reproductive outcomes in clinical practice.

Chronic endometritis (CE) is a chronic inflammatory condition of the endometrium characterized by plasma cell infiltration of the endometrial stroma. The condition is frequently asymptomatic or associated with nonspecific symptoms, which may contribute to underdiagnosis in women with infertility. Increasing evidence suggests that CE may negatively affect endometrial receptivity, embryo implantation, and reproductive outcomes, including recurrent implantation failure and pregnancy loss.

The MORE study is a prospective cohort study designed to evaluate the prevalence, diagnosis, treatment response, and reproductive impact of CE in women undergoing infertility evaluation. The study will enroll women aged 18 to 40 years with diagnosed infertility who are scheduled for diagnostic hysteroscopy with endometrial biopsy. Approximately 100 participants are expected to be enrolled between January 2026 and December 2029.

The study will assess the prevalence of histologically confirmed CE using histopathological evaluation combined with immunohistochemical detection of plasma cells (CD138 staining). Hysteroscopic findings suggestive of CE, including endometrial hyperemia, stromal edema, micropolyps, and abnormal vascular patterns, will be systematically documented and correlated with histopathological results in order to evaluate the diagnostic value of hysteroscopic markers in routine clinical practice.

Participants diagnosed with CE will receive standardized antibiotic treatment according to institutional protocols. Following treatment, reproductive outcomes will be prospectively monitored for up to 12 months. Outcomes of interest include spontaneous conception, assisted reproductive technology (ART) outcomes, implantation rates, clinical pregnancy, ongoing pregnancy, live birth, and miscarriage rates. Pregnancy-related complications, including preeclampsia, placental disorders, premature rupture of membranes, preterm birth, and delivery complications, will also be evaluated in participants who achieve pregnancy.

The study will additionally investigate the relationship between the endometrial microbial environment and reproductive outcomes. Endometrial samples obtained during hysteroscopy may be analyzed to characterize microbial profiles associated with CE and treatment response. Particular attention will be paid to microorganisms previously associated with CE, including Escherichia coli, Enterococcus faecalis, Corynebacterium species, Klebsiella pneumoniae, Mycoplasma species, and sexually transmitted pathogens.

A retrospective control cohort will include infertile women who previously underwent hysteroscopy with endometrial biopsy. Archived endometrial tissue samples from these participants will undergo additional immunohistochemical evaluation for CE in order to compare reproductive outcomes between participants with and without histological evidence of CE.

Clinical, demographic, reproductive, laboratory, imaging, and treatment-related data will be collected from electronic medical records and entered into a secure REDCap database using structured electronic case report forms. Collected variables will include demographic characteristics, infertility history, prior ART treatment, hysteroscopic findings, histopathological and immunohistochemical results, antibiotic treatment details, reproductive outcomes, pregnancy complications, and neonatal outcomes.

Data quality assurance procedures will include structured data entry forms, predefined variable definitions, range and consistency checks, and periodic review of entered data by authorized study investigators. Source data verification will be performed using electronic medical records and pathology reports. All study data will be pseudonymized using unique study identification codes. Direct participant identifiers will be stored separately from study data in accordance with institutional data protection procedures and General Data Protection Regulation (GDPR) requirements. Access to the REDCap database will be restricted to authorized study personnel only.

The planned statistical analysis will primarily be descriptive. Results will be reported as absolute numbers, percentages, and 95% confidence intervals. Comparisons between subgroups will be performed using chi-square or Fisher exact tests for categorical variables and t-tests or Mann-Whitney U tests for continuous variables, depending on data distribution. A p-value below 0.05 will be considered statistically significant. Missing or incomplete data will be documented and analyzed according to predefined statistical procedures.

The study will be conducted in accordance with the Declaration of Helsinki, Good Clinical Practice (GCP) principles, and GDPR requirements. The protocol and related study documents will be submitted for approval to the Ethics Committee of University Hospital Královské Vinohrady (FNKV), Prague, Czech Republic.

Inclusion Criteria

• Female participants aged 18-40 years.
• Diagnosis of infertility (primary or secondary infertility).
• Indication for diagnostic hysteroscopy with endometrial biopsy as part of infertility evaluation.
• Suspected or confirmed chronic endometritis.
• Ability and willingness to provide written informed consent prior to any study-related procedures.
• Willingness to undergo protocol-defined antibiotic treatment.
• Willingness to comply with study procedures and follow-up assessments.
• Agreement to reproductive outcome monitoring following treatment, including spontaneous conception and pregnancies achieved through assisted reproductive technologies (ART).

Exclusion Criteria

• Age >40 years.
• Current pregnancy.
• Known hypersensitivity or contraindication to tetracycline antibiotics or other study-related antibiotic therapy without a suitable alternative treatment option.
• Severe systemic disease or medical condition that, in the opinion of the investigator, could interfere with study participation, safety, or interpretation of study results.
• Active malignant disease requiring systemic treatment.
• HIV infection or other severe immunodeficiency disorder.
• Acute pelvic inflammatory disease or clinically significant active genital tract infection requiring immediate treatment.
• Previous participation in this study.
• Inability to undergo planned hysteroscopy or endometrial biopsy.
• Inability or unwillingness to comply with study procedures or follow-up requirements.
• Failure or refusal to provide written informed consent.

The study population will consist of women aged 18-40 years with primary or secondary infertility undergoing diagnostic hysteroscopy with endometrial biopsy for infertility evaluation or suspected chronic endometritis (CE). Participants will be recruited at University Hospital Královské Vinohrady and collaborating reproductive medicine centers in Prague, Czech Republic. Eligible participants must provide written informed consent and agree to protocol-defined diagnostic procedures, antibiotic treatment if indicated, and prospective follow-up of reproductive outcomes. The study will include women with previous unsuccessful assisted reproductive technology (ART) cycles, recurrent implantation failure, recurrent pregnancy loss, or unexplained infertility. Approximately 100 participants are expected to be enrolled.