Periodontal Pathogens and Inflammatory Biomarkers in Missed Abortion

This is a prospective, matched case-control observational study conducted at Necmettin Erbakan University. The study population will consist of pregnant women followed at the Department of Obstetrics and Gynecology. Participants will be enrolled after providing written informed consent.

The study is planned to include 160 participants: 80 pregnant women diagnosed with missed abortion and 80 pregnant women with an ongoing uncomplicated pregnancy. Control participants will be matched to cases according to age within approximately 2 years and gestational age within approximately 1 week.

Women aged 18 to 40 years at 20 weeks of gestation or earlier will be eligible. Participants with detected fetal chromosomal or genetic abnormalities, current smoking or alcohol use, diabetes mellitus, hypertension, autoimmune disease, antibiotic use within the previous 3 months, induced abortion, or multiple pregnancy will be excluded.

For the missed abortion group, saliva sampling and periodontal examination will be performed after the diagnosis of missed abortion has been confirmed and before uterine evacuation, curettage, or medical treatment. For the control group, saliva samples and periodontal measurements will be obtained during routine pregnancy follow-up.

Unstimulated whole saliva will be collected before periodontal examination to minimize contamination related to probing-induced bleeding. Salivary periodontal pathogen burden will be evaluated using quantitative real-time polymerase chain reaction. The target microorganisms will include Porphyromonas gingivalis, Fusobacterium nucleatum, and Tannerella forsythia. Salivary concentrations of IL-1β, IL-6, TNF-α, MMP-8, and prostaglandin E2 will also be assessed using validated immunoassay methods.

Serum samples will be obtained only from residual blood remaining after routine clinically indicated obstetric laboratory testing. No additional venous blood collection will be performed solely for research purposes. Serum levels of CRP, IL-1β, IL-6, TNF-α, MMP-8, and prostaglandin E2 will be evaluated.

Routine complete blood count parameters will also be recorded. These data will be used to calculate systemic inflammatory indices, including the neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, mean platelet volume-to-platelet ratio, and systemic immune-inflammation index.

A comprehensive periodontal examination will be performed, including probing pocket depth, clinical attachment level, bleeding on probing, gingival index, plaque index, gingival recession, tooth mobility, furcation involvement, and missing tooth status.

In the missed abortion group, routine genetic examination results from abortus material will be reviewed. Genetic assessment performed as part of routine clinical care includes evaluation of selected autosomal chromosomes and sex chromosomes using qPCR/QF-PCR and STR-based methods, together with assessment for maternal cell contamination. Cases with detected fetal chromosomal abnormalities or unreliable fetal genetic results will not be included in the main analysis.

Participants in the control group will be followed through routine obstetric records to verify continuation of pregnancy through at least 20 weeks of gestation and, when feasible, through 24 weeks. Participants who develop missed abortion, spontaneous abortion, detected fetal chromosomal abnormality, or a major obstetric complication before the predefined confirmation point will be excluded from the control-group analysis.

The primary objective is to assess the relationship between periodontal infection and missed abortion after exclusion of detected major fetal chromosomal abnormalities. Additional objectives are to compare local and systemic inflammatory biomarkers between groups and to investigate associations among periodontal pathogen burden, periodontal clinical status, inflammatory mediators, and prostaglandin E2.