FRIDAY, Aug. 26 (HealthDay News) -- Women with dental cavities who deliver their babies by Caesarean section should pay close attention to their babies' dental health later on, a new study suggests.

Researchers from New York University found that a cavity-causing bacterium that grows on tooth surfaces appeared much earlier in babies delivered by C-section than in those delivered vaginally. The study evaluated 156 mother-infant pairs.

"We are the first to report that there is a link between C-sections and the acquisition of cavity-causing bacteria in the baby," said Dr. Yihong Li, an associate professor of basic science and craniofacial biology at the New York University College of Dentistry.

Li, who is lead author of the study, added that the researchers did not study whether the babies delivered by C-section actually got more cavities later, but only that they had more cavity-causing bacterium earlier.

The study appears in the September issue of the Journal of Dental Research.

The reason for the findings? Li suspects that vaginally delivered infants, because of exposure to a greater variety and intensity of bacteria from their mothers and the surrounding environment at birth, develop more resistance to the cavity-causing germ than do C-section babies, who have less bacterial exposure at birth.

The women in the study were mostly black women from an inner-city area of Birmingham, Ala. In all, 127 of the women had vaginal deliveries and 29 had C-sections. Their mean age was approximately 21 years, and about 75 percent of the women had cavities. Li and her team then started collecting saliva and plaque samples from the babies to evaluate them for bacterium.

The bacterium, Streptococcus mutans, was detected in 55 of the 156 infants, on average at 22.3 months of age. But the C-section infants acquired the germ at 17.1 months of age, compared to 28.8 for the vaginally delivered babies.

Dr. Edmond Hewlett, an associate professor of dentistry at the University of California, Los Angeles School of Dentistry and a consumer advisor for the American Dental Association, called the study sound.

"What's new here is the association between the time of infection with bacteria that cause cavities and the type of delivery," he said. It has been known that the primary route of infection for cavity-causing bacteria is mother to infant, he said.

Even so, the new study findings "shouldn't affect the decision for women to have a C-section," Hewlett added.

The take-home message for mothers, Li said, is this: "If the mother has very poor oral health, she really needs to pay attention to her [baby's oral health] if she delivers C-section."

"Don't share spoons with your baby," Hewlett tells mothers, especially those who have cavities. "Chewing gum with Xylitol in it after eating is a good way to clear the mouth of bacteria."

More information

To learn more about preventing cavities, visit the American Dental Association.