The aims of this study are:

1. To assess the prevalence of prematurity, especially early prematurity, among T1D patients, and compare it to the prematurity prevalence among the non-diabetic general population in Israel.
2. To characterize epidemiological and clinical factors that differ between premature-born patients that developed T1D and those that have not, including the nutritional and therapeutic properties in NICU.

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.

In the latter part of the study, a multi-centered, paired case-control study is performed.

Preterm born T1D patients will be paired to matched non-diabetic children at a ratio of 3:1, according to medical center, sex, gestational week of birth, season and year of birth. Data collected includes: ethnicity, family history of autoimmune diseases, age and type of first enteral nutrition, and pharmacological exposures.

Inclusion Criteria:

1. Patients diagnosed with T1D
2. Patients treated in one of the 13 participating centers
3. For the case-control portion of the study, all children born between 1.1.1990-31.12.2013 and admitted to NICU medical centers that have been included in the original cohort portion
4. Patients for whom a complete medical record is available

Exclusion Criteria:

1. Lack of birth data
2. Unknown type of diabetes
3. For case control portion, an incomplete medical record/inadequate documentation

All T1D patients in Israel, born during 1990-2013 and diagnosed prior to January 2015, time of data collection. Inclusion criteria included all patients diagnosed as T1D by a pediatric endocrinologist according to the American Diabetes Association criteria, and treated for their T1D with insulin. Patients are identified from registries of the 13 participating centers.

IPD data will not be available for anyone other than the PI and co-investigators.