Evidence Links Mother's Oral Health to Health of Her Newborn
Pregnant women with high levels of an oral bacterium associated
with tooth decay and caries are at risk for delivering preterm low
birth weight (PLBW) babies, according to a study that was published
in the February issue of the Journal of Periodontology. The study
marks the first time that preterm delivery has been associated with
oral bacteria other than those which cause periodontal disease.
This new evidence adds to the growing body of research which shows
that a pregnant woman's oral health is important to the health of
The study's principal investigator, Dr. Ananda P. Dasanayake, Associate
Professor of Epidemiology & Health Promotion and Director of the
Graduate Program in Clinical Research, hypothesizes that oral bacteria
associated with caries can travel to the uterus as transient bacteria.
Once in the uterus, the bacteria and the molecules the body produces
in response to them (known as proinflammatory mediators) can lead
to uterine contractions and cervical dilation. When the cervix becomes
dilated, more bacteria can enter and eventually cause the uterine
membranes to rupture and preterm birth to occur.
Preterm low birth weight is generally defined as delivery before
37 complete weeks of pregnancy with a birth weight of less than
2,500 grams. PLBW babies have a greater risk of morbidity, mortality,
and disability. Preterm deliveries rose 27 percent between 1982
and 2002, to a total of 480,812, or 12.1 percent of all U.S. births,
an increase attributed to such factors as the growing use of fertility
drugs, increasing teenage pregnancy and smoking levels, and physicans'
improved ability to successfully deliver high-risk pregnancies that
might otherwise have ended in miscarriage. It has been estimated
that hospital-related costs for each preterm delivery were about
$75,000 in 2002 -- representing a total cost of approximately $36
billion, according to the March of Dimes and other organizations
that track pregnancies. PLBW is the second leading cause of infant
death in general, and the major cause of infant mortality among
Using bacterial samples of 297 predominantly African-American women
in Birmingham, Alabama, Dr. Dasanayake's team examined the effect
of cariogenic and other bacteria on pregnancy, and found that high
levels of Actinomyces naeslundii genospecies 2, an oral bacterium
associated with dental caries, were significantly associated with
low birth weight and preterm delivery. A tenfold increase in bacterial
levels was associated with a 60 gram decrease in birth weight and
a nearly 0.17 week (1.19 days) decrease in the length of the pregnancy.
The co-investigators on the study were Dr. Yihong Li, Associate
Professor of Basic Science and Craniofacial Biology; Dr. Howard
Wiener, a Postdoctoral Fellow at the University of Alabama School
of Public Health; Dr. John D. Ruby, an Associate Professor at the
University of Alabama at Birmingham School of Dentistry; and Dr.
Men-Jean Lee, an Associate Professor of Obstetrics and Gynecology
and a reproductive scientist at NYU School of Medicine.