Preterm delivery of low-birth-weight infants (PLBW) remains a significant public health issue and a leading cause of neonatal death and long-term neurodevelopmental disturbances and health problems. Recent epidemiological and microbiological immunological studies have suggested that periodontal disease may be an independent risk factor for PLBW. Postulated mechanisms include translocation of periodontal pathogens to the fetoplacental unit and action of a periodontal reservoir of lipopolysaccharides or inflammatory mediators. However, non-causal explanations for the correlation between periodontitis and PLBW can also be offered. Prospective studies, and eventually interventional studies, will be necessary before periodontitis can be considered as a causal factor for PLBW.