Background: Many studies have reviewed the relationship between clinical and subclinical infections and preterm birth. As a result, the inflammatory response to chronic subclinical infection has been used regularly in the etiology of preterm birth. Macones and colleagues conducted a randomized trial to assess the potential benefit of treating destructive periodontal disease in pregnant women to reduce the incidence of spontaneous preterm birth.

The Study: Pregnant women between six and 20 weeks of gestation were recruited from prenatal care clinics for the study. Gestational age and singleton pregnancy were verified by dates and ultrasound assessments. Women already receiving periodontal treatment and those who had used antibiotics or antimicrobial mouthwash were excluded from the study, as were women with mitral valve prolapse. The assessment for periodontal disease was based on an initial screening by nurses followed by a secondary screening of potential cases by dental hygienists. Women with attachment loss of at least 3 mm on three or more teeth were eligible for the study. Dental faculty members assessed 10 percent of participants at each site to monitor eligibility.

Study participants were randomly assigned to receive scaling and root planing (active treatment) or superficial cleaning (control). Routine prenatal care was provided to all participants. Obstetric physicians and staff were blinded to the study allocation of individual patients. The primary outcome was spontaneous preterm birth, defined as delivery before 35 weeks of gestation as a result of idiopathic preterm labor or preterm rupture of the amniotic membranes.

Results: One half of the more than 3,500 women screened met the criteria for periodontal disease. Of the 756 available participants, 376 were randomly assigned to scaling and root planing and 380 to superficial cleaning. The groups were comparable in gestational age, severity of periodontal disease, and history of preterm delivery. The average age of study participants was 24 years, 87 percent were black, and 85 percent were single. Twenty-nine percent of the active treatment group and 35 percent of the control group had some form of college education. Approximately one half of all participants had moderate to severe periodontal disease.

Spontaneous preterm delivery occurred in approximately 10 percent of women from each group, and the average gestational age at delivery (38 weeks) was also similar. No statistically significant differences were noted in other pregnancy outcomes, including mean birth weight, proportion of low– or very low–birth-weight infants, stillbirths, and measures of neonatal morbidity and mortality. A trend towards increased risk of preterm births indicated for maternal or fetal complications was noted in the active treatment group. Subgroup analysis showed an increased risk of preterm births in multiparous mothers assigned to active treatment, but no differences in nulliparous participants by study assignment. Increased risk of preterm birth was also noted in the active treatment group for women with a history of preterm birth and women with more severe periodontal disease.

Conclusion: The authors of this study found no evidence of improved pregnancy outcomes in mothers undergoing active periodontal treatment. The finding of a trend towards increased premature births in women receiving treatment for periodontal disease contrasts with reports of benefits from previous studies. Although differences in study populations and design may explain the differences in findings, the possibility that treatment of periodontal disease during pregnancy could increase the risk of premature birth is concerning.