title: Serum 25-hydroxyvitamin D level during early pregnancy and type 1 diabetes risk in the offspring.
abstract: OBJECTIVE
  Vitamin D deficiency during the fetal period or infancy is one of the suggested environmental factors for type 1 diabetes and for its increasing incidence. To test this hypothesis we compared serum 25-hydroxyvitamin D (25(OH)D) levels during early pregnancy in mothers of children who subsequently developed type 1 diabetes (case mothers) with mothers of non-diabetic healthy children (control mothers) of the same age.
  
  
  METHODS
  Children with type 1 diabetes were identified from the nationwide prescription register. 25(OH)D concentration was measured from serum samples collected during the first trimester of pregnancy from all Finnish women (Finnish Maternity Cohort). A total of 343 case mothers and 343 control mothers were included in the study. Samples were collected throughout the year. Samples from case and control mothers were matched on the day of collection.
  
  
  RESULTS
  Mean 25(OH)D levels in case mothers (43.9 nmol/l) and control mothers (43.7 nmol/l) were not different. Of all mothers, 481 (70.1%) were vitamin D-deficient or -insufficient.
  
  
  CONCLUSIONS
  No difference was found in serum 25(OH)D concentrations during first trimester of pregnancy between mothers whose children later on developed type 1 diabetes, and mothers of non-diabetic ' healthy' children of the same age. It is difficult to detect possible effects of mothers' vitamin D deficiency during early pregnancy on the development of type 1 diabetes in the offspring in this population, as such a large proportion of mothers were vitamin D-deficient or -insufficient.
authors.affiliation: Department of Public Health, University of Helsinki, Helsinki, Finland. maija.miettinen@thl.fi
authors.forename: M E
authors.initials: ME
authors.lastname: Miettinen
authors.forename: L
authors.initials: L
authors.lastname: Reinert
authors.forename: L
authors.initials: L
authors.lastname: Kinnunen
authors.forename: V
authors.initials: V
authors.lastname: Harjutsalo
authors.forename: P
authors.initials: P
authors.lastname: Koskela
authors.forename: H-M
authors.initials: HM
authors.lastname: Surcel
authors.forename: C
authors.initials: C
authors.lastname: Lamberg-Allardt
authors.forename: J
authors.initials: J
authors.lastname: Tuomilehto
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007223:Infant; D011247:Pregnancy / Q000097:blood*; D011261:Pregnancy Trimester, First / Q000097:blood; D012306:Risk; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D