Incidence and clinical risk factors of Bednar's aphthae in Japanese newborns

Background: The etiology of Bednar's aphthae remains unclear. Our aim was to investigate the incidence of, and factors associated with, Bednar's aphthae in a Japanese newborn cohort.Methods: A retrospective cross-sectional study was conducted on neonates discharged from the well-baby nursery at Saitama City Hospital, Japan. The principal investigator carefully examined each neonate's oral cavity, up to and including the pharynx, with a light-emitting diode (LED) headlight to determine the presence of Bednar's aphthae. Maternal and neonatal clinical characteristics were first compared between neonates with and those without Bednar's aphthae by univariate analysis. Variables with significant inter-group differences upon univariate analysis were entered into a multivariable logistic-regression model.Results: This study enrolled 1996 infants. We observed Bednar's aphthae in 9.3% of the Japanese newborn infants who were included. When restricted to infants who were born via vaginal delivery, 13.2% of them had aphthae. Multivariable logistic regression analysis identified vaginal delivery (odds ratio = 6.19, p < 0.0001) in Model 1, and vaginal delivery (odds ratio = 6.73, p < 0.0001) and birth weight (odds ratio = 0.9995, p = 0.034) in Model 2 as independent risk factors for the disease.Conclusion: This is the first report of the prevalence of Bednar's aphthae among Japanese neonates. Vaginal delivery was identified as the strongest risk factor. Although confounding between mode of delivery and mechanical stimuli associated with sucking was not found in this study, the findings pave the way for a better understanding of the etiology of Bednar's aphthae.