Objective: Maternal periodontitis has been suggested as an important risk factor for preterm low birth weight. The aim of the present observational study was to assess whether full-mouth therapy of periodontitis in pregnant women reduces the risk of preterm low birth weight. Method and Materials: From April 2006 to April 2007, 302 pregnant women who were at less than 22 weeks of gestation were invited to attend a periodontal examination. Consent for periodontal screening was given by 62 mothers; 54 of them met criteria. Consent for periodontal treatment was provided by 12 patients (group 1), whereas 14 patients declined therapy (group 2). No periodontal therapy was indicated in 28 patients (group 3). Nonsurgical treatment was performed in group 1 as full-mouth disinfection between 22 and 30 weeks of gestation. Periodontal reevaluation was performed 4 to 6 weeks later. As primary outcome, the gestational age at the end of pregnancy was assessed in all groups. Secondary outcomes were birth weight and growth restriction. Results: Periodontitis treatment improved periodontal measures (P = .001) in this rather small collective. However, there were no statistically significant differences between treatment group 1 and group 2 in the gestational age, birth weight, or growth restrictions. There were also no statistically significant differences compared to group 3. Conclusions: In consideration to the limited number of patients, full-mouth therapy in pregnant women can improve periodontitis but does not significantly alter the gestational age at birth or birth weight. Therefore, new studies are needed in this field especially with respect to the genetic disposition of mothers to chronic or aggressive periodontal inflammation response. Keywords: gestational age at birth, maternal, nonsurgical periodontal therapy, periodontitis, preterm low-birth-weight infants