Maternal periodontal disease also has been associated with other adverse pregnancy outcomes such as preeclampsia, gestational diabetes, fetal loss, and low birth weight. In a “clinical expert series” on maternal oral health in pregnancy published in 2008, Dr. Boggess provides a comprehensive summary of the literature on these associations, and details why good oral health should be a goal for all individuals, including pregnant women (Obstet. Gynecol. 2008;111:976–86).
Treatment and Preterm Birth
While some of the initial studies of periodontal treatment in pregnancy were promising, suggesting that treatment may reduce the risk for preterm birth, we now have three large studies in the United States that have been negative. Each has involved randomization to active treatment with scaling and root planing or placebo treatment, and each has shown no significant difference in preterm birth between the two groups.
In the multicenter Periodontal Infections and Prematurity Study (PIPS) trial reported early this year, we screened more than 3,500 women between 6 and 20 weeks' gestation and found a prevalence of periodontal disease of 50%. (We defined periodontal disease as attachment loss of at least 3 mm on at least three teeth. Moderate to severe disease was defined as attachment loss of 5 mm or more on three or more teeth.)
The 756 women with periodontal disease who returned for the scheduled treatment visit were then randomly assigned in a 1:1 ratio to active treatment or placebo (superficial cleaning). The mean gestational age at screening was 13.1 weeks, and the mean gestational age at treatment was 16.5 weeks. The groups were balanced with respect to gestational age, periodontal disease severity, and history of preterm delivery (Am. J. Obstet. Gynecol. 2010;202:147.e1–8).
There was no significant difference between the two treatment groups in the incidence of spontaneous preterm birth at less than 35 weeks' gestation (our primary end point) or at less than 37 weeks' gestation. We also saw no difference in mean birth weight or the proportion of low-birth-weight or very-low-birth-weight newborns. There also was no difference in composite neonatal morbidity/mortality between the groups.
These findings are largely concordant with those of two other recent studies. In one study published in 2006, more than 800 women were randomly assigned to receive either antepartum periodontal treatment (before 21 weeks' gestation) or postpartum treatment (control). Periodontal treatment improved measures of periodontitis but did not significantly alter the risk of preterm delivery at less than 37 weeks' gestation (N. Engl. J. Med. 2006;355: 1885–94).
The other study – coined the MOTOR study (Maternal Oral Therapy to Reduce Obstetric Risk) – randomized more than 1,800 patients at three sites to periodontal treatment early in the second trimester or delayed treatment after delivery. Again, investigators demonstrated improvements in oral health after treatment, but found no significant reduction in preterm birth at less than 37 weeks of gestation (Obstet. Gynecol. 2009;114:551–9).
Current Thinking
What should we do in the wake of these negative findings?
First, we must realize that periodontal treatment in these trials improved the oral health of pregnant women, and that the benefits of good oral health cannot be disputed. Secondly, we must still appreciate – and share with our patients – that periodontal disease is very common and does appear to be associated with preterm birth (and possibly other adverse pregnancy outcomes), as well as with other negative health outcomes such as cardiovascular disease and diabetes.
We should be careful, however, and be sure to tell patients that treatment of periodontal disease alone does not appear to reduce the risk of preterm birth.
We need to study these associations further and better understand the mechanisms of periodontal disease–associated preterm birth. There also are unanswered questions about treatment. For example, is it possible that treatment prior to pregnancy may reduce the risk of preterm birth? Is it possible that using adjuvant antibiotic mouthwash may improve pregnancy outcomes? Questions such as these should be answered with additional clinical trials.
We also must better understand and delineate reported disparities in oral health. Periodontal disease disproportionately affects racial and ethnic minorities and those of low socioeconomic status. While differences in access to care and other behaviors and practices likely play a role in these disparities, experts believe that there also may be population differences in oral microbiology or inflammatory responses to bacterial colonization.
As we wait for more information, we can tell our patients about the importance of good oral health, and we can reassure them that periodontal disease treatment in pregnancy appears to be safe. We are not ready, however, to recommend routine screening and treatment of periodontal disease in pregnancy to improve pregnancy outcomes.