Aim: This narrative review evaluated the current evidence in relation to the plausible
biological mechanisms between periodontal disease and pregnancy complications. 

Material and methods: Data available mainly from clinical-association and intervention
studies, along with microbiological and immunological findings, were included. 

Results & conclusions: The current data support the role of periodontal inflammation along
with mainly Gram-negative disease-provoking microbes in the etiopathogenesis of APOs.
However, because of their multi-factorial nature, the outcomes are not yet conclusive and the
association between bacterial colonisation and maternal immunological responses remains
speculative. Furthermore, understanding the exact mechanisms – why some women develop
APOs in the presence of a periodontal inflammatory burden while others do not – remains to
be achieved.