BackgroundCaesarean-section (C-section) may influence children’s long-term health by affecting bacterial colonization. However, few studies have focused on the association between C-section delivery (CSD) and dental caries, and previous conclusions have been conflicting. This study aimed to explore whether CSD would increase the risk of early childhood caries (ECC) in preschool children in China.MethodsThis study was a retrospective cohort study. Three-year-old children with full primary dentition were included through the medical records system. Children in the nonexposure group were vaginally delivered (VD), while children in the exposure group were delivered through C-section. The outcome was the occurrence of ECC. After agreeing to participate in this study, guardians of included children completed a structured questionnaire on maternal sociodemographic factors, children’s oral hygiene and feeding habits. The chi-square test was used to determine differences in the prevalence and severity of ECC between the CSD and VD groups and to analyse the prevalence of ECC according to sample characteristics. Subsequently, potential risk factors for ECC were preliminarily identified through univariate analysis, and the adjusted odds ratios (ORs) were further calculated through multiple logistic regression analysis after controlling for confounding factors.ResultsThe VD group included 2115 participants while CSD group included 2996 participants. The prevalence of ECC was higher in CSD children than in VD children (27.6% vs. 20.9%,P< 0.05), and the severity of ECC in CSD children was higher (mean number of decayed, missing, and filled teeth, dmft: 2.1 vs. 1.7,P< 0.05). CSD was a risk factor for ECC in 3-year-old children (OR = 1.43, 95% CI = 1.10–2.83). In addition, irregular tooth brushing and always prechewing children’s food were risk factors for ECC (P< 0.05). Low maternal educational attainment (high school or below) or socioeconomic status (SES-5) may also increase the prevalence of ECC in preschool children and CSD children (P< 0.05).ConclusionsCSD would increase the risk of ECC in 3-year-old Chinese children. Paediatric dentists should devote more attention to the development of caries in CSD children. Obstetricians should also prevent excessive and unnecessary CSD.