there are three stories in this series:

• disease that invades from the mouth
• can a mother's bad gums reduce her baby's weight?
• do healthy gums mean a healthier heart?

Can a Mother's Bad Gums Reduce Her Baby's Weight?

by michelle coppedge

One in ten U.S. babies is born too small or too early. We know about the effects of premature birth: health and developmental problems for the infants as they grow up, several billion dollars in neonatal intensive care costs each year. But could the health of their mothers' gums be one of the causes?

Research in the last few years has strongly suggested that it is, and now researchers are trying to learn whether treating gum disease, or periodontal disease, in expectant mothers can reduce risks of preterm delivery and growth restriction in their babies.

"The rate of preterm delivery has not decreased at all in the last forty years," says Steven Offenbacher, professor of periodontology in the School of Dentistry. "Obstetrics has a long history of things that seem associated with preterm birth — but when you try to intervene, nothing happens," adds his colleague, James Beck, professor of dental ecology in the dentistry school.

This time, though, the two researchers and their U.S. and international colleagues think they've found a way to make something happen. Two recent pilot studies, one in Chile and one at the University of Alabama, showed that mothers who were treated for periodontal disease were less likely to give birth prematurely to low-birth-weight babies. In the study done by Néstor López at the Universidad de Chile, pregnant women with periodontal disease received treatment either before twenty-eight weeks of gestation or after delivery. The women who were treated during pregnancy were five times less likely than those in the control group to give birth to preterm, low-birth-weight babies.

And this past year Offenbacher, Beck, and colleagues began work on a five-year clinical intervention involving 1,800 mothers. It's a multicenter trial with sites at UNC-Chapel Hill, Duke, the University of Texas at San Antonio, and the University of Alabama. "We'll be treating mothers who have periodontal disease to see if it reduces the rate of preterm delivery," Offenbacher says. "Periodontal disease is a potentially modifiable risk factor. In other words, it's something we can manage."

Steven Offenbacher and James Beck in the General and Oral Health Center. "The rate of preterm delivery has not decreased at all in the last forty years," Offenbacher says. Photo by Steve Exum; click to enlarge.

Offenbacher originated an area of research called periodontal medicine, a term he first used in 1997 to identify the field of dentistry focused on oral infection's effects on systemic — or overall — health, leading to problems such as premature delivery and growth restriction. Before coming to Carolina, when Offenbacher was working as a dentist at Emory University, the prenatal clinic referred a lot of patients to him. Many of these expectant mothers were in their late teens and early twenties, much earlier than chronic periodontal disease usually develops.

"I became interested in the connection and the many inflammatory processes that were involved with preterm delivery," Offenbacher says. "There were connections not only from the clinical context, but also anecdotally from patients."

When Offenbacher arrived at Carolina, he teamed up with epidemiologist Beck and others to investigate these relationships. The Center for Oral and Systemic Diseases (COSD), a multidisciplinary research unit of the School of Dentistry that involves investigators from the Schools of Medicine and Public Health, was established in April 1998. Preliminary studies, including a case-control study at Carolina and a five-year collaborative study with Duke University researchers called OCAP (Oral Conditions and Pregnancy), confirmed that mothers who have periodontal disease, and whose periodontal disease progresses during their pregnancy, are at a greater risk of having babies who are born too small and too early. Kim Boggess, an obstetrician formerly at Duke who is now assistant professor of obstetrics and gynecology at Carolina, also published a paper from the OCAP study linking periodontal disease with preeclampsia, a toxic condition that can develop in late pregnancy.

So how does infection in a woman's mouth affect the fetus growing inside her? To find out, Offenbacher and Beck are studying animals as well as humans. "The animal models have been giving us a better feel for what's actually going on — the mechanisms that may be involved, what oral organisms may be playing a role," Beck says.

Their studies with animals have shown that a couple of particularly invasive bacteria present in an infected mouth — Porphyromonas gingivalis and Campylobacter rectus — seem to target the fetus in utero. These bacteria are hardy, adapted to living in the oral cavity and surviving all the white blood cells' efforts to kill them. "And periodontal disease itself creates a wound or an area that enables the organisms to get into the bloodstream and create some of the health problems we associate with pregnancy," Offenbacher says.

In their studies with mice, the researchers found high levels of antibody to these oral bacteria in the fetal cord blood of underdeveloped pups. No evidence of the organisms was present in the placentas of normal pups.

"So it's spreading, it's getting to the individual fetus, and it's causing inflammation — we can measure biochemical changes of inflammation that are going on," Offenbacher says. "We think there may be similar mechanisms involved in humans."

Campylobacter species have been linked in veterinary medicine to other problems with pregnancy, including increased risk for stillbirth and miscarriage. And the human strain of Campylobacter rectus seems to have the same ability as the mouse strain to move through the bloodstream to the placenta.

Offenbacher, Beck, and their colleagues are convinced that this is happening — convinced enough that they are ready to see what they can do to stop it. With their current five-year clinical study, they want to prove that treating periodontal disease is key to making healthy, full-term pregnancies more likely.

"We've moved beyond these associations now to see if we can treat gum disease and prevent abnormal pregnancies," Offenbacher says.

The OCAP study received funding from the National Institute of Dental and Craniofacial Research, as did Offenbacher's and Beck's current clinical study. Contact the GO (General and Oral) Health Center at (919) 966-5271 or gocenter@dentistry.unc.edu for more information on current clinical studies linking periodontal disease with premature birth and growth restriction as well as heart disease. The GO Health Center is the clinical research facility of UNC-Chapel Hill's Comprehensive Center for Inflammatory Disorders (CCID) and Center for Oral and Systemic Diseases (COSD).