Objectives: To assess whether the effect of providing mothers with guidance during pregnancy and when the child was 6 and 12 months old, which had drastically reduced the prevalence of early childhood caries at 20 months of age, would be sustained at 6-7 years of age. Methods: Children, whose mothers had been enrolled in a randomized controlled trial during pregnancy and a comparison group of similar school children, were examined for the presence of caries by the South Australian School Dental Services (SA SDS) at 6-7 years of age. Results: Of 625 eligible trial participants, 277 (44%) participated in the follow-up and dental records were available for 187 of them (30%). Loss to follow-up and reasons for it were similar in the intervention and control groups. At 6-7 years of age, 33% of children in the trial had caries compared with 42% in the SA SDS comparison group (n = 263). All measures of caries severity (d 3mft, d 3mfs and SiC 30) were lower, but not significantly so, in the intervention than in the control group. Children in the comparison group of school children had more severe caries than those in the trial (P < 0.01) and in the intervention group especially (P < 0.005). Children in both randomized groups suffered significantly less toothache than those in the comparison group (P < 0.001). Conclusions: Providing new mothers with guidance on caries prevention helps to reduce early childhood caries and has a sustainable effect up to school age.