Pregnant women with serious gum disease appear to have an increased risk of delivering prematurely, but whether this condition actually triggers early labor remains unclear, according to a new study.

Researchers found that among 139 women who gave birth at their center, those with severe gum disease were about three times more likely than other women to have a premature delivery.

Gum disease is caused by bacteria that dwell in the plaque that forms on the teeth. It can range from the mild inflammation and occasional bleeding of gingivitis to a more-serious stage where the gums pull away from the teeth and the bones and other supporting structures of the teeth begin to decay, potentially leading to tooth loss.

The new findings are in line with past studies that have linked severe gum disease to preterm birth, as well as low birth weight, fetal growth restriction and certain other pregnancy complications.

Similarly, other research has tied gum disease to the risk of heart attack stroke. Scientists have suggested that the explanation for all of these links rests in the movement of gum disease bacteria. If these bugs enter the blood circulation, they may trigger damaging inflammation elsewhere in the body - including in the placenta.

However, in the new study, Dr. Alice R. Goepfert at the University of Alabama at Birmingham and colleagues found no association between gum disease and markers of inflammation in the upper genital tract at the time of delivery.

This casts some doubt on the theory that gum disease bacteria spread to the placenta to trigger early labor, Dr. Goepfert said.

So while there does appear to be a relationship between severe gum disease and preterm labor, she told Reuters Health, it’s not clear whether it’s a “cause-and-effect” relationship.

Goepfert and her colleagues report their findings in the October issue of the journal Obstetrics & Gynecology.

The researchers studied 59 women entered spontaneous labor before the 32nd week of pregnancy, 44 who went full-term, and 36 who had labor induced early due to complications. All of the women had a dental exam within a few days of giving birth, and the researchers analyzed the placenta and umbilical cord blood for bacteria and certain markers of inflammation.

They found that 49 percent of the women who went into spontaneous preterm labor had severe gum disease, compared with 25 percent to 30 percent of the other women.

When the researchers considered other factors, such as age, race, education and smoking, they found that severe gum disease was still linked to a roughly three-fold greater risk of premature delivery.

According to Goepfert, it’s possible that gum disease does not actually spur preterm labor, and that instead, the two may be linked by some third, as yet known, factor.

A clinical trial is currently underway to see whether treating gum disease lowers the risk of preterm delivery, Goepfert noted.

“That question will hopefully be answered soon,” she said.

SOURCE: Obstetrics & Gynecology, October 2004.