Association of periodontitis with preterm birth and low birth weight: a comprehensive review

It is estimated that six million perinatal deaths occur every year worldwide, with premature birth being the main cause. Scientific evidence has shown that there is an association between periodontal health during pregnancy and adverse outcomes of labor, although interventional studies based on the treatment of periodontitis have failed to document an impact on reducing the incidence of preterm birth (PB) or low birth weight (LBW). Two pathogenic mechanisms have been proposed to explain this association. The direct pathway is based on the presence of gram-negative anaerobic bacteremia originating in the gingival biofilm, whereas the indirect pathway involves the production of pro-inflammatory markers which enter the bloodstream from the gingival submucosa. The result is the same: the development of an immune inflammatory response and/or the local suppression of growth factors in the fetal-placental unit, which in turn triggers labor. In the present review, we describe current concepts pertinent to PB and LBW, chronic and aggressive periodontitis, and the most frequent aspects of periodontal pathology during pregnancy. We evaluate the scientific evidence available to date, and offer a detailed description of the two pathways proposed to explain the association of maternal periodontitis with preterm and LBW delivery.