Fall/Winter 2005 Table of Contents
     
Research in Focus
Link Found Between C-Section Delivery
and Higher Risk of Cavities in Newborns
 


Yihong Li, DDS, MPH, PhD


















Three progressively enlarged views of Streptococcus mutans bacterial colonies in a culture dish.
A new study by NYU dental researchers suggests that women with dental caries who deliver Cesarean-section babies should pay special attention to their newbornsí oral health.

The NYU researchers focused on a caries-causing bacterium that mothers with caries transmit to their newborns. Known as Streptococcus mutans, the bacterium grows on tooth surfaces and in spaces between teeth just above the gingival margin, where it multiplies and converts foods, especially those containing sugar and starch, into acids that break into the tooth surface.

C-section deliveries were infected by the bacterium almost a year earlier than vaginally delivered infants in the four-year study of 156 mother-infant pairs published in the September issue of the Journal of Dental Research. The first signs of the bacterium appeared at an average of 17.1 months of age in C-section babies, compared to 28.8 months in vaginally delivered infants, a significant finding since previous studies have linked earlier bacterial infection with a higher rate of dental caries in children.

NYUís study is the first to distinguish between bacterial infection in C-section and vaginally delivered babies. The findings suggest that mothers who have dental caries should inform their family dentists if they had a C-section delivery because of the potentially higher risk that the child will also develop caries, said the studyís principal investigator, Dr. Yihong Li, an Associate Professor of Basic Science and Craniofacial Biology at NYU College of Dentistry.

"Vaginally delivered infants offer oral bacteria a less hospitable environment", Dr. Li explained. "They develop more resistance to these bacteria in their first year of life, in part because of exposure to a greater variety and intensity of bacteria from their mothers and the surrounding environment at birth. C-section babies have less bacterial exposure at birth, and therefore less resistance."

Mothers in Dr. Liís study who delivered C-section babies had high levels of Streptococcus mutans infection and caries on an average of one-third of their teeth. A majority had an annual family income of $10,000 or less--a potential barrier to accessing dental care--and a history of sexually transmitted disease. These cofactors contributed to an earlier onset of bacterial infection, Dr. Li said.

The study followed a predominantly African-American group of women from an inner-city area of Birmingham, Alabama, beginning in their third trimester of pregnancy. There were 127 vaginal and 29 C-section births.

Further study in a broader cross-section of the population is needed to determine if C-section births can be linked to earlier acquisition of this and other oral bacteria and if a higher incidence of caries follows. The results of Dr. Liís study add to a growing body of knowledge about a possible link between a motherís level of tooth decay and her newbornís health that was identified by NYU dental researchers in an earlier study of predominantly low-income African-American women in Birmingham, which found that pregnant women with high levels of oral bacteria associated with dental caries are at risk for delivering preterm low birth weight babies. Published last February in the Journal of Periodontology, that study was led by Dr. Ananda P. Dasanayake, an Associate Professor of Epidemiology & Health Promotion. Dr. Dasanayake is among a group of researchers in the U.S. and abroad who also have reported that periodontal diseases in pregnant women may be a risk factor for delivering preterm low birth weight babies.

Dr. Liís coinvestigators on the C-section study were Dr. Dasanayake; Dr. Page W. Caufield, a Professor of Cariology and Comprehensive Care at NYU College of Dentistry; Dr. Howard W. Wiener, a Research Assistant at the School of Public Health at the University of Alabama at Birmingham; and Dr. Sten H. Vermund, a Professor of Epidemiology at the University of Alabama.