Oral Microbiome and Preterm Birth: Correlation or Coincidence? A Narrative Review

BACKGROUND: Physiological changes that occur during pregnancy involve, as a natural consequence, also modifications of oral microbiome. However, the addition with microbial imbalance due to pre-existing periodontal infection might impair a pathological alteration in the phylogenetic community structure and composition in the oral cavity, exacerbating an inflammatory status, and becoming a potential risk factor for preterm birth. From the empirical findings about the relationship between periodontal pathogens and systemic diseases, a clear interest focused on the potential impact of some periodontal pathogens on the preterm birth risk has emerged. AIM: Exploration of the potential interdependence existing between dysbiosis of oral microbiome and changes in maternal-fetal barrier in premature rupture of membranes. MATERIALS AND METHODS: In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a Medline search was performed for studies focusing on oral microbioma and its association with pre-term birth, and completed by additional hand searching. Two reviewers independently selected studies and extracted data. The search was restricted to only reports written in English. RESULTS: The electronic search produced 66 items. Six duplicates were found. Among the collected studies, 56 were discarded because they met the exclusion criteria. The articles and reports in our review showed a connection between preterm birth and altered oral microbiome, suggesting a potential key role of Fusobacterium nucleatum, a notable periodontal pathogen involved in several pathological periodontal conditions, in increasing the risk of premature birth. CONCLUSIONS: Since F. nucleatum is frequently associated with preterm birth, it is coherent to hypothesize a potential role for the oral microbiota for preterm birth risk. Further studies should be carried out to determine the changes of the oral microflora in pregnancy and to provide comprehensive knowledge of the diversity of oral bacteria involved in preterm birth.