ObjectiveTo investigate the demographic features of labial adhesion (LA) in South Korea.DesignA population-based nationwide study.SettingCensus population of South Korea.ParticipantsWith the entire population of South Korea (n=47 990 761), patients under age 7 who were newly diagnosed with LA from January 2010 to December 2014 were included.Main outcome measureThe average incidence and the peak age of LA occurrence were estimated.ResultsA total of 4934 newly diagnosed LAs were analysed. The incidence of LA has constantly increased since 2008, the year that the Korean Developmental Screening Test for InfantsandChildren registry began. The average incidence of LA was 55.0 cases/100 000 person-years (95% CI 53.5 to 56.6). The highest incidence was 183.6 cases/100 000 person-years (95% CI 175.8 to 191.6) in the age group of13 to 24 months. The relative risk of acquiring LA in the age group of 13 to 24 months was 1.481 (95% CI 1.381 to 1.587) compared with the age group of 0 to 12 months.ConclusionsThe demographic characteristics of LA including the average incidence and the highest incidence age group in South Korea were revealed in this nationwide, population-based study including a total of 4934 newly developed LA cases. Further studies are needed to reveal the natural disease course and the significance of diagnosing asymptomatic LA cases.