A national cohort study, including linkage of data from 13 pediatric diabetes centers and Israeli National Registries, including all patients with T1D born during 1990-2013. Data collected includes: ethnicity, gestational age, birth season, age and season at T1DM diagnosis, and presence of autoimmunity in family. The prevalence of prematurity among T1D is compared to the non-diabetic general population registry of 2000-2013. Additional comparisons are between T1D patients born term and preterm, aimed to unveil specific influencing clinical and epidemiological factors.