Spring 2005 Table of Contents
     
Research in Focus
Study Equates Caries Bacteria With Preterm Birth Risk
 

Dr. Ananda Dasanayake
New 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 her newborn.

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 African-American infants.

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.