There are few up to date studies suggesting hypothesis of the risk increasing influence of active periodontitis on a premature labor, intrauterine growth retardation and finally delivering a baby with a low birth weight. In the majority of these papers a risk of premature labor was directly proportional to the degree of periodontitis during the early pregnancy. Unfortunately these were retrospective or not randomized. The present study presents a prospective evaluation of the influence of periodontal lesions on the course of otherwise normal pregnancies.