By Jane E. Brody
Published: October 9, 1196
Although it may seem improbable, infection in the gums of a pregnant woman may lead to a more than sevenfold increase in her risk of delivering a premature baby of low birth weight, according to findings published yesterday in The Journal of Periodontology.
The study suggests that untreated periodontal disease may account for a large share of premature births for which no other explanation can be found.
The research team of periodontists, obstetrician-gynecologists and epidemiologists emphasized that their findings, based on a detailed analysis of 124 births, were preliminary and needed to be confirmed by “larger prospective multicenter investigations.” Nonetheless, they estimated from their findings that periodontal infection might be responsible for as many as 18 percent of the 250,000 premature babies that are born weighing less than 5.5 pounds in the United States each year.
If such births could be prevented by proper periodontal care and treatment of periodontal disease in women of childbearing age, the researchers said, premature births might be reduced by about 45,500 each year at a savings of almost $1 billion in intensive neonatal care.
Dr. Steven Offenbacher, the lead author of the new report, said in an interview: “A prenatal visit to a periodontist is a reasonable thing to do at this point. Any infection in a pregnant women should be a concern. When you have periodontal disease, even eating an apple or brushing your teeth can release bacteria and their toxins into the bloodstream.”
An unpublished study conducted a decade ago at Harvard University’s Forsyth Dental Clinic found a similar relationship between periodontal disease and preterm births, said Dr. James McGregor, a professor of obstetrics and gynecology at the University of Colorado in Denver.
“This new study is just fascinating,” Dr. McGregor said. “It goes along with the findings that other infections — urinary tract infections and pneumonia, for example — increase the risk for preterm birth. And we have shown that you can decrease preterm births by 50 percent if you treat common reproductive tract infections like bacterial vaginosis and chlamydia.”
In the newly published report, Dr. Offenbacher and his colleagues at the University of North Carolina and Meharry Medical College in Nashville explained how an infection in the mouth might interfere with the development of an unborn child and lead to premature labor. They noted that other kinds of bacterial infections in pregnant women that had been linked to premature births did not necessarily involve infections of the fetus or placenta.
Rather than directly attacking the fetus, the bacteria appear to retard fetal growth by releasing toxins into the woman’s bloodstream that reach the placenta and interfere with fetal development. In addition, the infection stimulates the woman’s body to produce inflammatory chemicals, similar to those used to induce abortion, that can cause the cervix to dilate and set off uterine contractions.
Dr. Offenbacher, a professor of periodontics at the University of North Carolina School of Dentistry in Chapel Hill, noted that in studies of pregnant hamsters, localized infection on the animal’s back with the bacterium Porphyromonas gingivalis, an organism commonly associated with periodontal disease, retarded fetal growth and reduced fetal weight up to 25 percent.
A co-author, Dr. Vern Katz, an obstetrician now specializing in maternal-fetal medicine at Sacred Heart Medical Center in Eugene, Ore., said, “We are finding more and more that the chemicals released in response to infection can lead to changes in the timing of birth and to premature rupture of membranes,” precipitating preterm labor and delivery.
But direct infection of the tissues of pregnancy may also be involved, said Dr. Robert Goldenberg, chairman of obstetrics and gynecology at the University of Alabama in Birmingham. “It’s clear to many of us that most preterm births, especially those that occur before 32 weeks of pregnancy, appear to be related to infections in the mother,” Dr. Goldenberg said. “And if you look carefully, you can actually find the organisms in the placenta, the chorionic membrane or the amniotic fluid.”
Participants in the current study were women who had received prenatal care at the University of North Carolina Hospitals. The researchers assessed the extent of periodontal disease in 93 women who had delivered premature babies of low birth weight and a comparable group of 31 women who gave birth to infants of normal weight. Without knowing the outcome of the women’s pregnancies, periodontists examined six sites per tooth in each woman’s mouth to determine how far periodontal disease had progressed.
The women who had delivered premature, low-birth-weight babies were found to have significantly worse periodontal disease than those whose babies were born at term at normal weight.
All told, the researchers concluded, after taking other possible causes of prematurity into account, that the risk of having a premature baby of low birth weight was at least 7.5 times as high for women with severe periodontal disease as it was for women with lesser degrees of periodontal infection.
Dr. James Beck, an oral epidemiologist on the research team, said, “The extent of disease in these mothers was quite a bit worse than you’d find in the general population of women of childbearing age.”
Dr. Roberto Romero, chief of perinatal research for the National Institute of Child Health and Human Development, said that if periodontal disease increased the risk of prematurity by seven times, “it could be one of the most important identifiable risk factors for preterm birth,” which he said occurred in 5 spercent of pregnancies and cost the country $5.7 billion a year.
Dr. Romero said the new study was important because it showed that an infection distant from the genital tract might significantly increase the risk of premature birth and because the infection involved was both identifiable and treatable.
To be sure that there was no other obvious explanation for their findings, the researchers factored into their analysis every established cause of premature birth, including smoking, use of alcohol and illicit drugs, lack of prenatal care, low socioeconomic status, prior history of premature birth and the presence of other infections or illnesses.
They uncovered no other reason for the relationship they had found between serious periodontal infection and premature low birth weight, although Dr. Offenbacher said it was still possible that periodontal disease was merely a marker for some other factor that was the direct cause. They did, however, find that the extent of periodontal disease was strongly linked to a previous delivery of a premature low-birth-weight baby as well as to premature delivery in the current pregnancy.
Dr. Beck, who is also at the University of North Carolina School of Dentistry, said the team would next like to conduct a larger study and to examine whether treating periodontal disease would reduce premature births.
“The current study revealed an association that seems to be real, but it is not a useful association unless we can intervene to improve the outcome of women’s pregnancies,” he said.
Periodontal disease can often be prevented by nightly flossing and regular, thorough cleaning of the teeth by a dentist, periodontist or dental hygienist. To reverse established periodontal infection, Dr. Offenbacher said, a periodondist has to scrape pockets of disease from the surface and roots of the teeth and sometimes has to remove infected gum tissue. Treatment with an antibiotic like Augmentin may also be prescribed. If left untreated for years, periodontal infection gradually erodes the bones in the jaw and causes the teeth to loosen and fall out.
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