Prenatal vitamin D levels could be tied to an increased risk of cavities in infants and toddlers. 134 mothers were examined prenatally, and then their children were evaluated at about the age of one year.
In a study of 134 expectant mothers, “about a third of the women were deficient in vitamin D, 22 percent of the infants had deficient or thinning enamel and 23 percent had cavities. After controlling for other factors, they found that the lower the prenatal vitamin D level in the mother, the higher the number of cavities in the child. Defective enamel and prenatal vitamin D levels were both independent predictors of cavities.” The New York Times Blog
While there were some problems with the study (for example, the study was not randomized), it does give some insight on one way to possibly prevent tooth decay in infants and toddlers.