RESUMO
OBJECTIVE: To clarify the characteristics of milestone achievement of Japanese infants using data assessed and recorded in real time via a Web-based app by caregivers. STUDY DESIGN: Between 2014 and 2019, the achievement of developmental milestones of 16 627 Japanese infants were recorded via the mobile app Papatto Ikuji along with pertinent information including sex, birth date, anthropometric measurements, and information on feeding. The milestones consisted of 20 items belonging to 4 domains: personal-social, fine motor-adaptative, language, and gross motor. The distribution of age at milestone achievement was compared with 4 conventional normative data. Subgroup analyses according to sex, season of birth, and feeding methods were performed with restricted mean survival time analysis. RESULTS: Age distributions of milestone achievement were generally similar in the app-based and conventional data. The exception was "Smile responsively," for which the age at achievement seemed higher in the app-based data. Subgroup analyses showed female-dominant sex differences in the achievement of person-social and language milestones. The results also showed seasonality in achievement of gross motor milestones, with earlier achievement in infants born in winter compared with those born in summer. CONCLUSIONS: We describe mobile app-based data on developmental milestone achievements that were recorded in real time. The app-based data were generally comparable with conventional normative data, suggesting that its potential to assess the development of children in real time. This could be used complementarily with the current well-child visits at scheduled time points.