Poor oral health is not only associated with diabetes and cardiovascular disease but adverse pregnancy outcomes. However the influence of dental caries on pregnancy is unknown. The aim of this study was to evaluate the association between dental caries and adverse pregnancy outcomes and the effect of treatment for dental caries on adverse pregnancy outcomes. Primiparas who delivered a singleton between January 1, 2010 and December 31, 2014 and underwent both general health examination and oral health examination during a National Korea Health Screening Examination within 1 year of pregnancy were eligible. The data of the women who met the inclusion criteria were linked to the data of their offspring contained within the National Korea Health Screening Program for Infants and Children database. Among 120,622 women who delivered during the study period, 28,623 (23.7%) women had dental caries. Among them, 4,741 (16.6%) women were treated for dental caries after diagnosis. In a multivariable analysis, women with dental caries had an increased risk of delivering large-for-gestational-age infants (odds ratio, 1.15; 95% confidence interval, 1.07, 1.23) compared to those without dental caries. When women with dental caries were divided on the basis of the treatment of dental caries, women with dental caries but no treatment had an increased risk of delivering large-for-gestational-age infants (odds ratio, 1.15; 95% confidence interval, 1.06, 1.24); conversely, there was no increased risk in women with dental caries and treatment compared with those without. Dental caries and its treatment were not associated with preterm birth and preeclampsia. Untreated dental caries was not associated with preterm birth or preeclampsia but with the risk of delivering large-for-gestational-age infants. These whole observation may be attributed to the various characteristics of mothers who develop dental caries are not treated.