Periodontitis in Pregnancy

When Is a Clinical Question Settled?

Marjorie Jeffcoat, DMD


May 04, 2011

In This Article

The Debate: Does Periodontal Disease Lead to Preterm Birth?

Questions linger about how (or if at all) periodontal disease influences systemic conditions (eg, diabetes, heart disease, and pregnancy outcomes). For this potential influence, known as the "oral-systemic link," research has generated enough evidence to be intriguing but not enough to be conclusive. This state of affairs, in which the proof or refutation of an important hypothesis seems to lie just over the horizon, is exciting for researchers. However, it poses a frustrating conundrum for clinicians, who need to make decisions now.

As one who wears the hats of both clinician and researcher, I've been giving some thought to the questions, "When can a research question be considered settled for the purpose of clinical decision-making, and what do we do in the meantime?"

Consider the link that has been purported to exist between periodontal disease and pregnancy outcomes.

  • Is it real?

  • Is it causal? and

  • Is it clear and strong enough to be factored into a plan of care?

The Evidence: Periodontal Disease and Preterm Birth

We are close to answering these questions, but right now, looking objectively at the evidence, we have no alternative but to consider this issue not quite settled. What must happen to settle the issue, or to estimate how close we are to doing so?

Adverse pregnancy outcome (eg, spontaneous preterm birth [sPTB] and low birth weight) is not only a high-priority health issue but also one of the easiest to study. In contrast to diabetes and heart disease, which take decades to develop, most pregnancies are completed within 9 months. Well-designed, adequately powered, ethical prospective studies shouldallow us to settle the question of the oral-systemic link (as it relates to pregnancy) in only a few years.

However, no such studies have been completed, and debate has arisen about the validity and utility of existing meager source data. A brief review of the literature indexed by PubMed revealed that review articles and meta-analyses on this topic outnumbered original research by a 3-to-1 margin! In other words, 3 papers were written about the topic for every paper that presented original data. In this case, published reviews of the literature can overwhelm the actual study data. Is this a rush to judgment?

Epidemiology 101: An Association?

The first hurdle in establishing a relationship between periodontal disease and the incidence of sPTB is epidemiologic and statistical: Does A make B more (or less) likely? At least 31 studies of this type have been reported. Most are case-control studies with as many as 3000 participants. The preponderance of the evidence (22 of 31 studies) shows that patients with periodontal disease are at greater risk for sPTB.[1] We can conclude that an association does exist, and this issue is settled.

Epidemiology 102: A Dose/Response Relationship?

If either the independent variable (periodontal disease) or the outcome can be quantified, epidemiologic data can be analyzed to determine something about the strengthof the association. We commonly refer to this as a dose/response relationship. Some of the studies cited above were designed to analyze this point and found a dose/response relationship between the severity of periodontal disease and sPTB. Another point is therefore settled, and we can proceed to the next hurdle.

A Fork in the Road

At this point, research takes 1 of 2 major directions. For some investigators, the presence of a dose/response prompts a search for a mechanism that is common to the disease and the outcome. Others are interested in the more immediate clinical question of whether periodontal treatment can reduce the incidence of sPTB. Both approaches are valid, and both are being actively pursued in parallel. My own approach falls into the latter group; we'll pursue that path.


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