Abstract: 　Objective To investigate the screen media use time in children under 3 years old in Shanghai， and to examin the association and the dose-effect relationship between screen exposure and language development. Methods　We performed a cross-sectional population-based study, children and their caregivers from 8500 families in Shanghai were recruited. Every family was asked to complete a specially-designed questionnaires covering demographic information, family socioeconomic status, and children’s language development milestones. Results　The prevalence of language developmental delay in one year and two years old children is 36.6% and 15.2% respectively. And it is higher in boys than girls, showing consistency with a previous study. Duration of screen media exposure was extending with age in children under three years old. Stratified analysis by the gender showed a negative correlation between the duration of screen exposure and expressive language development in both genders (P<0.05). Stratified analysis by age showed that when the children were under 18 months, the more hours spending with the screen media, the poorer ability of expressive language (P<0.05). Whereas, for the children older than 18 months, the effect only occurred when the duration of screen media exposure is more than one to two hours per day. Conclusions　Our findings showed the deleterious impact of screen media in infant’s expressive language development. Screen media shouldn’t be used by children under 18 months. Guidance and alternatives to screen media use should be available to families in pediatric practices.

Key words: screen media exposure;　language development;　infants