The evidence for an association between adverse pregnancy outcomes and periodontitis is as follows:
- Plausibility – current evidence supports the idea that oral microorganisms and their products enter the blood circulation and travel directly to the fetal environment where they cause inflammatory and immune responses affecting the feto-placental unit. These bacteria in the circulation may also circulate to the liver, where inflammatory agents are produced, which in turn then circulate to the developing fetus.
- Epidemiology – in clinical studies, low birth weight, pre-term birth and pre-eclampsia have all been associated with the presence of periodontitis in the mother, when all other risk factors have been accounted for. However, the strength of the connection found between periodontitis and these pregnancy outcomes varies between studies, and some show no association. The heterogeneity of data is likely due to differences in the study designs, study populations and different methods used for assessing and classifying periodontal disease.
- Intervention studies – results from clinical trials have shown that, in general, scaling and root debridement carried out during the second trimester of pregnancy, with or without antibiotic therapy, does not significantly improve adverse pregnancy outcomes, such as preterm birth and low birth weight. However, some clinical trials did report a favorable effect overall and it is possible certain populations of pregnant women may benefit from periodontal therapy, even though others will not. One reason for negative study results may be the interaction between periodontitis and pregnancy outcomes is more complex than our current understanding and the study results may have been affected by the type and timing of treatment employed and by the types of patients selected.