By David A. Albert, D.D.S., M.P.H.
Columbia University College of Dental Medicine

Each year, about 12% of babies born in the United States enter the world too soon (prematurely). These "preterm" infants are born before the 37th week of pregnancy. Many have low birth weight. This is defined as less than 2,500 grams (about 5.5 pounds). About 1% to 2% of all births are low birth weight.

Preterm birth often leads to major problems. Low birth weight babies are more likely to die soon after birth. Those who survive have a higher risk of cerebral palsy. They are more likely to have problems with breathing, behavior, development and learning.

Preterm births cost society an estimated $26 billion each year in the United States.

Researchers have tried for many years to figure out why preterm births occur, and how to prevent them. Statistics show that certain factors increase the risk of preterm birth:

• Being pregnant with more than one baby
• Having a history of premature birth
• Having an abnormal cervix or uterus
• Having an infection during pregnancy
• Smoking or using illicit drugs
• Receiving little or no prenatal care
• Being underweight

Some studies suggest that periodontal disease may increase the risk of preterm birth and low birth weight. Periodontal disease is an infection. It damages the gums and other structures that support the teeth. The body controls an infection with inflammation response. This response may be one reason for early rupture of the birth membranes ("water breaking") and preterm birth.

Women with periodontal disease are more likely to have premature babies. More than a dozen studies have shown this. Only a few studies have looked at whether treating periodontal disease reduces the risk of premature birth.

One recent study was carried out in four states (Mississippi, New York, Kentucky and Minnesota). It examined the effects of treating periodontal disease during pregnancy. In this study, treatment did not improve overall birth outcomes The investigators did find a pattern suggesting that periodontal treatment might help reduce the risks of stillbirths and miscarriages.

Another recent study was conducted in Alabama, North Carolina and Texas. This study also found that periodontal treatment did not improve birth outcomes.

These two studies provided care during pregnancy. It is possible that periodontal treatment started in pregnancy comes too late. Treatment may have to occur before a woman conceives to prevent any pregnancy problems. Future studies should examine if earlier periodontal treatment improves birth outcomes.

Do these studies mean that periodontal disease does not affect the risk of preterm birth or low birth weight? No, two studies are not enough to prove that there is or is not a direct link between gum disease and birth outcomes.

Three other studies of this type have already been done. Two of them found that pregnant women who got periodontal treatment had a lower risk of preterm birth. One study did not find that treatment helped.

It is too early to say that periodontal disease is a cause of preterm birth or low birth weight. Larger studies need to be done.

What should a woman of childbearing age do? My advice is to maintain good oral health, particularly healthy gums.

Good oral health is important, whether or not it affects the outcome of pregnancy. In fact, women with healthier mouths have been shown to have children with healthier mouths as well. That by itself is a good reason to treat tooth decay and periodontal disease as early as possible.

David A. Albert, D.D.S., M.P.H., is an associate professor and associate director of community health at the Columbia University College of Dental Medicine. He also holds an appointment in the Joseph Mailman School of Public Health at Columbia University. He maintains a practice within the ambulatory care network of the Columbia DentCare program in the community of Washington Heights/Inwood in Northern Manhattan.