Abstract: Objective：To understand the changing trend of the birth weight of live births in Tianjin city during 2008—2015 and to provide the basis for the control of birth weight in a reasonable range. Methods：Selection of mothers living in the six areas of Tianjin city（Heping District, Hedong District, Hexi District, Nankai District, Hebei District, Hongqiao District）, who delivered between October 1, 2007 to September 30, 2015 of pregnant full 28 weeks of live births as the research object, describe the changing trend of birth weight, the incidence of low birth weight and large infant. Results：Between 2008 and 2015, there were significant differences in the average birth weight, low birth weight rate and the occurrence of the large infant in the urban areas of Tianjin in different years (F=17.306, P＜0.001; χ2=72.684, P＜0.001; χ2=92.818, P＜0.001). The average birth weight and the incidence of large infant in the urban area of Tianjin in 2009 was the highest, 2010 decreased year by year, a slight increase in 2015. The incidence of low birth weight was lowest in 2009, 2010 increased year by year. Conclusions：Tianjin city birth weight has been decreased from 2008 to 2015, but still higher than the reference value recommended by the World Health Organization, birth weight control is still key point of perinatal health care in Tianjin city.

Key words: Infant，newborn, Birth weight, Tianjin, Epidemiologic studies, Infant，low birth weight, Fetal macrosomia