Some infants delivered by Cesarean section may have a higher risk of developing cavities later in life, a new study suggests.

Researchers found that among young children who harbored a particular cavity-causing bacterium in their mouths, those who were delivered by Cesarean section acquired the infection one year earlier, on average, than those delivered vaginally. Mothers appeared to be the main source of transmission of the bacterium, known as Streptococcus mutans.

Since early acquisition of S. mutans, which can make cavity development more likely, the findings suggest that these children could be at greater risk of cavities down the road.

That’s not certain, since the study did not follow the children long enough, lead study author Dr. Yihong Li told.

Still, she said the “take-home message” is that women with cavities who deliver by Cesarean section should pay particularly close attention to their children’s oral health over time.

Li, an associate professor at the New York University College of Dentistry, and her colleagues report the findings in the Journal of Dental Research.

The researchers suspect that vaginal delivery offers infants some early protection against S. mutans colonization. Passing through the birth canal exposes newborns to “good bacteria” from their mothers that are key to setting up infants’ defense against disease-causing bugs. These beneficial bacteria set up colonies that leave little space for less benign sorts like S. mutans.

But because Cesarean section deliveries are relatively aseptic, these infants may be more vulnerable to early S. mutans colonization, Li explained.

For their study, she and her colleagues followed 156 mainly African-American mothers and their infants for 4 years. All of the women were low-income and three quarters had cavities.

Overall, the researchers detected S. mutans in 35 percent of the children over the study period. Those who were delivered by Cesarean section first showed the bacterium at the age of 17.1 months, on average, versus 28.8 months among children who were delivered vaginally.

The age gap is important, Li said, because other research has suggested that earlier S. mutans acquisition increases a child’s cavity risk.

But “mode of delivery” was only one of the variables that affected a child’s acquisition of S. mutans, Li pointed out. Among the other factors were the extent of a mother’s Tooth decay and the level of S. mutans in her saliva.

The study adds to recent research that has highlighted the potential importance of a mother’s oral health to her child. Several studies, for example, have linked maternal gum disease, which is caused by bacteria, to poorer fetal growth and a higher risk of preterm delivery and certain other pregnancy complications.

SOURCE: Journal of Dental Research, September 2005.