BACKGROUND.  Early in life, vaginally delivered infants exhibit a different composition of the gut flora compared with infants delivered by caesarean section (C-section); however, it is unclear whether this also applies to the oral cavity. AIM.  To investigate and compare the oral microbial profile between infants delivered vaginally and by C-section. DESIGN.  This is a cross-sectional case-control study. Eighty-four infants delivered either vaginally (n = 42) or by C-section (n = 42) were randomly selected from the 2009 birth cohort at the County Hospital in Halmstad, Sweden. Medically compromised and premature children (<32 weeks) were excluded. The mean age was 8.25 months (range 6-10 months), and parents were asked to complete a questionnaire on socioeconomic factors, lifestyle, and hygiene habits. Saliva was collected and analysed using checkerboard DNA-DNA hybridization. RESULTS.  A higher prevalence of salivary Streptococcus salivarius, Lactobacillus curvata, Lactobacillus salivarius, and Lactobacuillus casei was detected in infants delivered vaginally (P < 0.05). The caries-associated bacteria Streptococcus mutans and Streptococcus sobrinus were detected in 63% and 59% of all children, respectively. CONCLUSION.  A significantly higher prevalence of certain strains of health-related streptococci and lactobacilli was found in vaginally delivered infants compared with infants delivered by C-section. The possible long-term effects on oral health need to be further investigated.

Within the limitations of this observational cohort study, caries prevalence in 3-year-old children was not related to the mode of delivery. However, the tendency of more severe caries in the C-section group justifies further studies, preferably with a prospective design.