title: Gestational Age and Birth Weight and the Risk of Childhood Type 1 Diabetes: A Population-Based Cohort and Sibling Design Study.
abstract: OBJECTIVE
  We investigated the effects of gestational age, birth weight, small for gestational age (SGA), and large for gestational age (LGA) on risk of childhood type 1 diabetes.
  
  
  METHODS
  We conducted a population-based cohort study of all singleton live births in Sweden between 1973 and 2009 and a sibling control study. Perinatal data were extracted from the Swedish Medical Birth Register. Children with type 1 diabetes diagnosis were identified from the Swedish National Patient Register. Log-linear Poisson regression and conditional logistic regression were used for data analysis.
  
  
  RESULTS
  The study cohort consisted of 3,624,675 singleton live births (42,411,054 person-years). There were 13,944 type 1 diabetes cases during the study period. The sibling control study consisted of 11,403 children with type 1 diabetes and 17,920 siblings. Gestational age between 33 and 36 weeks (relative risk [RR] 1.18 [95% CI 1.09, 1.28) and 37 and 38 weeks (RR 1.12 [95% CI 1.07, 1.17]) was associated with type 1 diabetes in the cohort study and remained significant in the sibling control study. SGA (RR 0.83 [95% CI 0.75, 0.93]) and LGA (RR 1.14 [95% CI 1.04, 1.24]) were associated with type 1 diabetes in the cohort study. The SGA association remained unchanged in the sibling study, while the LGA association disappeared. Very low birth weight was associated with a reduced risk of type 1 diabetes.
  
  
  CONCLUSIONS
  The findings suggest a small association between gestational age and type 1 diabetes that is not likely due to familial confounding factors. Gestational age and type 1 diabetes may be related to insulin resistance due to early life growth restriction or altered gut microbiota in preterm babies.
authors.affiliation: Department of Epidemiology and Public Health, University College Cork, Cork, Ireland The Irish Centre for Fetal and Neonatal Translational Research, Department of Obstetrics and Gynaecology, University College Cork, Cork, Ireland a.khashan@ucc.ie.
authors.forename: Ali S
authors.initials: AS
authors.lastname: Khashan
authors.affiliation: The Irish Centre for Fetal and Neonatal Translational Research, Department of Obstetrics and Gynaecology, University College Cork, Cork, Ireland.
authors.forename: Louise C
authors.initials: LC
authors.lastname: Kenny
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lundholm
authors.affiliation: Department of Epidemiology and Public Health, University College Cork, Cork, Ireland.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Kearney
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Tong
authors.initials: T
authors.lastname: Gong
authors.affiliation: Centre for Biostatistics, Institute of Population Health, University of Manchester, Manchester, U.K.
authors.forename: Roseanne
authors.initials: R
authors.lastname: McNamee
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden Astrid Lindgren Children's Hospital, Lung and Allergy Unit, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Catarina
authors.initials: C
authors.lastname: Almqvist
mesh_terms: D000328:Adult; D001724:Birth Weight; D016022:Case-Control Studies; D002648:Child; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007236:Infant, Small for Gestational Age; D008297:Male; D011247:Pregnancy; D012042:Registries; D012307:Risk Factors; D035781:Siblings; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult