RESUMO
PURPOSE: The association between periodontopathogenic microbiota and preterm birth (PTB) has been overly studied. However, the biological mechanisms involved are little known. The objective is to evaluate the effect of periodontopathogenic bacteria burden (PBB), periodontal disease and other infections during pregnancy on preterm birth (PTB), through Structural Equation Modeling. METHODS: This was a case-control study nested in a prospective cohort called BRISA, including 330 pregnant women, 110 cases and 220 controls. This study included the following variables: cytokines interleukin-10 (IL-10) and transforming growth factor beta (TGF-ß), periodontal disease, PBB, age, socioeconomic status (SES), systemic infections and PTB. The correlations between variables were analyzed using Standardized Coefficient (SC). RESULTS: Greater PBB interfered positively with the occurrence of periodontal disease (SC: 0.027; p: 0.011), but these were not associated with the cytokines studied, nor with PTB. The lower serum levels of IL-10 (SC - 0.330; p 0.022) and TGF-ß (SC - 0.612; p < 0.001), and the presence of other systemic infections during pregnancy (SC 0.159; 0.049) explained the higher occurrence of PTB. CONCLUSION: It is possible that only the more severe periodontal disease and other systemic infections are capable of altering the cascade of cytokines regulating the inflammatory process and have an effect on the occurrence of PTB.