During the last 10–15 years, in an effort to improve troubling rates of spontaneous preterm delivery and other adverse pregnancy outcomes, investigators have looked at many kinds of clinical and subclinical infections and explored their possible associations to preterm birth.
Bacterial vaginosis is one infection that has been associated in numerous studies with a higher risk of preterm birth. Periodontal disease is another. While not all studies have found an association, there is substantial evidence – mainly from observational and epidemiologic studies – linking periodontal disease to spontaneous preterm birth and identifying the disease as a probable risk factor for preterm delivery.
One of the larger studies was a prospective cohort study involving more than 1,300 pregnant women who were enrolled at 21–24 weeks' gestation and provided information on various possible risk factors for preterm birth. Later analyses showed that women with moderate to severe periodontal disease were 4.5 times as likely to deliver spontaneously before 37 weeks' gestation, 5.3 times as likely to deliver before 35 weeks' gestation, and 7.1 times as likely to deliver before 32 weeks (J. Am. Dent. Assoc. 2001;132:875–80).
Other published studies report lower levels of risk, and a more recent meta-analysis that included 17 studies and more than 7,000 women suggested a 2.8-fold increased risk of preterm birth in women with periodontal disease (Am J. Obstet. Gynecol. 2007;196:135.e1–7).
Today, interestingly, we know that bacterial vaginosis and periodontal disease each present our patients with a similar magnitude of increased risk for preterm delivery: a two- to threefold increased risk.
Unfortunately, hopes that identifying and treating the conditions could reduce risk and improve pregnancy outcomes have been dashed – in both cases. In the case of periodontal disease, three major randomized controlled trials in the United States – including the Periodontal Infections and Prematurity Study (PIPS) published in February of this year – have provided evidence that screening and treating periodontal disease during pregnancy are not likely to reduce rates of preterm birth.
This does not mean, however, that we should ignore the problem of periodontal disease. It is a huge problem, affecting up to 40% of pregnant women according to most reports, and there is no evidence to suggest that dental examinations or treatment are deleterious during pregnancy. In all the studies that have been done over the last decade or so, there is nothing to suggest that we shouldn't look for periodontal disease and treat it.
Periodontal disease is clearly associated with other poor health outcomes, in addition to its association with preterm birth, and study after study has shown that good oral health is important for good overall health.
Despite our inability to reduce preterm birth rates with periodontal treatment, it is important to recognize the value of good oral health for all adults, including pregnant women.
The Disease and Its Effects
Periodontal disease often evolves from untreated gingivitis, which causes the gums to redden, swell, and bleed more easily. Bacterial plaque on the surface of the teeth spreads and grows below the gum line (dentistry speaks of a subgingival biofilm), adding to progressive gram-negative anaerobic infection of the mouth and inflammatory responses that ultimately lead to the destruction of tissue and bone.
As Dr. Kim A. Boggess has described in numerous articles on periodontal disease in pregnancy, damage occurs both directly from bacteria in plaque and indirectly through bacterial stimulation of local and systemic inflammatory and immune responses.
Interestingly, there is no single validated definition of periodontal disease. Instead, the clinical criteria used to define periodontal disease have varied among studies, which can make all the data difficult to interpret. Some investigators have focused on the magnitude and extent of attachment loss or other clinical measures of periodontal disease, whereas others hone in on measures of infection and host response to oral bacteria. There are commonly agreed upon clinical markers, however, including gingival recession, tooth attachment loss, and bleeding on gingival probing.
Much of the research into the role of maternal oral health in pregnancy outcomes has been driven by appreciation of the importance that oral health plays in overall general health, and by a growing recognition that periodontal disease can trigger chronic, systemic inflammation, which in turn can drive various disease processes.
The conditions most often associated with periodontal disease are cardiovascular disease and diabetes. Some studies published in the last decade have shown, for instance, that individuals with periodontal disease have at least a 1.5-fold increased risk of developing cardiovascular disease. There also is some evidence that treating periodontal disease can improve various measures of cardiovascular function – such as blood pressure and levels of inflammatory cytokines. In addition, some data suggest that periodontal treatment results in better diabetic control.