<p dir="ltr">This multicenter study investigated whether mode of delivery, breastfeeding duration, and dietary habits predict severe early childhood caries (S-ECC) in children under 3 years of age in Brazil and the United States. Data for this analysis were derived from the repository of the study entitled <i>“Mode of Delivery, Prolonged Breastfeeding and Diet as Predictors of Caries: a Multicenter Study in Children Under 3 Years.”</i> Using electronic medical records from 700 infants and toddlers examined between August 2021 and November 2023, the study collected information on delivery type, feeding practices, diet, oral hygiene, age, sex, and nationality. The overall S-ECC prevalence was high (59.4%), and bivariate analyses showed significant associations with vaginal delivery and a cariogenic diet. However, in the multivariable regression model, only older age, longer breastfeeding duration, and nationality (with U.S. children presenting higher dmft scores) remained independent predictors of S-ECC. These findings highlight the multifactorial etiology of early caries and emphasize the importance of early, culturally informed prevention strategies for children in this vulnerable age group.</p>