Pregnant women have extra incentive to brush, floss, and take good care of their teeth. Those simple steps could help their babies get a better start in life.

Bacteria in the mouth of the mother-to-be could influence the baby’s birth weight (search) and delivery date, says a new study. That’s important because babies born prematurely and/or at a low birth weight are more vulnerable to health problems, disability, and even death.

The preterm and low birth weight problem was put in sharp, startling detail earlier this year in a CDC report. The CDC found that infant deaths rose in 2002 for the first times since 1958, partly due to more babies being born too small and too soon.

“Birth weight is one of the most important predictors of an infant’s survival chances,” the CDC reported. The 2002 death rate for preterm infants was 15 times higher than that of full-term babies, according to the CDC.

Rates Rising

Today, most U.S. babies are not born prematurely (before 37 weeks of pregnancy) or at a low birth weight. Medical advances have made it possible to keep tiny babies alive that would almost certainly not have survived in past generations.

But the problem hasn’t gone away. Preterm low birth weight is still the second leading cause of infant death in general.

The numbers have increased in America over the last few decades. The preterm delivery rate rose from 10.2 percent to 11.6 percent of all live births from 1987-1998. Low birth weight increased for all races from 6.8 to 7.6 percent from 1980-2000.

Those numbers come from the latest study on oral health, preterm delivery, and low birth weight. The researchers included Ananda Dasanayake of New York University’s College of Dentistry.

Which Groups Have the Highest Rates of Preterm Delivery?

“These rates are at least two times higher among African Americans,” write Dasanayake and colleagues. In fact, preterm low birth weight is the major cause of infant mortality among African-American infants.

Overseas, even more preterm babies die young. Every year, about 4 million babies die before they’re 1 month old. Most are born in poorer countries that often lack sanitation and medical facilities expected in the West. Preterm birth is a leading cause, accounting for an estimated 28 percent of infant deaths worldwide. That’s according to a report published in The Lancet earlier this month.

Oral Health’s Role

Certainly, oral health (search) isn’t the only reason for preterm delivery or low birth weight. The mother’s overall health, resources, and prenatal care are crucial.

Still, bacteria seen in gum disease (search) and cavities may play a role. The mouth is home to hundreds of types of bacteria, some of which are linked to dental problems.

Recently, oral bacteria were studied in about 300 pregnant women in Alabama. Most of the women were black and lived in a low-income area in and around Birmingham. That reduced the influence of racial, social, or economic factors, say Dasanayake and colleagues.

The researchers monitored levels of several types of bacteria while the women were pregnant. They also noted the babies’ delivery date and birth weight.

Helpful, Harmful Bacteria

One type of bacteria — Actinomyces naselundii (search) – was linked to lower birth weight and earlier delivery. Another bacteria — Lactobacillus casei (search) — was associated with a slightly higher birth weight and delivery date.

Different kinds of lactobacillus bacteria are found elsewhere in the body. For instance, they help with digestion. Possibly, the lactobacillus bacteria in the women’s mouths helped keep the vaginal environment healthy, boosting the chances of a good delivery, says the study.

The researchers aren’t sure how that works. Possibly, “oral bacteria and the molecules the body produces against them can enter the uterine environment through the bloodstream and may influence the delivery process,” says Dasanayake in a news release.

Harmful oral bacteria have also been linked to greater risk of heart disease.A similar theory — oral bacteria that flow through the blood to other parts of the body — has been floated for that problem, too.

That’s all the more reason to reach for your toothbrush. Monitoring oral bacteria levels could help reduce poor pregnancy outcomes, the researchers conclude.

Their study appears in the Journal of Periodontology’s February issue.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Dasanayake, A. Journal of Periodontology, February 2005; vol 76: pp 171-177. WebMD Medical News: “Why The Infant Death Rate Went Up.” WebMD Medical News: “Simple Measures Could Save Millions Of Infants.” News release, American Academy of Periodontology. News release, New York University. WebMD Medical News: “Brush Your Teeth, Help Your Heart.”