Despite medical care improves consistently, the rate of preterm birth has risen in recent years. In Italy the rate of preterm birth between the XXXIII and the XXXVI week is 13.5%, while it amounts to 1.3% for preterm birth between XXIV and the XXXII week. Consequently, the identification of risk factors for preterm birth that might be modified would have far-reaching and long-lasting effects. A significant number of preterm birth may be attributed to infections of the urogenital tract, such as bacterial vaginosis. In the last decade, great interest has been generated to support the hypothesis that sub-clinical infection at sites that are also distant from the genito-urinary tract may be an important cause of preterm labour, probably through the activation of abnormal inflammatory responses within the uterus and intrauterine tissues. There is emerging evidence of a possible relationship between maternal periodontal diseases as a potential risk factor of adverse pregnancy outcomes, like preterm low birth weight even though not all of the actual data support such hypothesis. Further studies are clearly required to clarify the causes and/or relationships linking pathologic oral conditions and adverse pregnancy outcomes. So far, from a clinical standpoint, it would appear that the assessment of the periodontal status of pregnant women during an early pregnancy might be useful in providing an important indicator of risk for future obstetric complications.