Of the two birthing methods, vaginal and C-section, the latter is normally harder on the mother, who has her abdomen cut open, and seemingly easier on the baby, who doesn't have to squeeze through the narrow birth canal.
However, for mothers with dental cavities, a C-section birth might not be so easy on the baby's future teeth. According to a study done by researchers at New York University, C-section babies are more likely to get cavity-causing bacteria earlier and more frequently than vaginally-born babies.
The researchers think this has to do with exposure to bacteria at birth. Vaginally-born babies encounter many different types of bacteria when they're born, giving them a chance to develop resistance to a variety of infections early on. C-section babies, on the other hand, encounter far fewer varieties of bacteria. So there's a greater chance that they'll have less resistance to bacterial infection, including the type that can cause tooth decay.
The researchers allow that the people they studied, mostly low income women with spotty access to dental care, clearly limits the study. However, the potential link they found between c-section births and cavities is part of a growing body of evidence linking oral health to pregnancy and birth issues. Other studies have found that women with gum disease are more likely to deliver premature, low-birth-weight babies. More studies need to be done to determine how, exactly, oral hygiene affects infant development.
Meanwhile, though, there's enough evidence to suggest that it's important for expecting mothers to have their teeth checked.