title: Preconceptional and prenatal supplementary folic acid and multivitamin intake and autism spectrum disorders.
abstract: To evaluate whether early folic acid supplementation during pregnancy prevents diagnosis of autism spectrum disorders in offspring.
  
  
  
  Information on autism spectrum disorder diagnosis was obtained from the National Hospital Register and the Central Psychiatric Register. We estimated risk ratios for autism spectrum disorders for children whose mothers took folate or multivitamin supplements from 4 weeks prior from the last menstrual period through to 8 weeks after the last menstrual period (-4 to 8 weeks) by three 4-week periods.
  
  
  
  We did not find an association between early folate or multivitamin intake for autism spectrum disorder (folic acid-adjusted risk ratio: 1.06, 95% confidence interval: 0.82-1.36; multivitamin-adjusted risk ratio: 1.00, 95% confidence interval: 0.82-1.22), autistic disorder (folic acid-adjusted risk ratio: 1.18, 95% confidence interval: 0.76-1.84; multivitamin-adjusted risk ratio: 1.22, 95% confidence interval: 0.87-1.69), Asperger's syndrome (folic acid-adjusted risk ratio: 0.85, 95% confidence interval: 0.46-1.53; multivitamin-adjusted risk ratio: 0.95, 95% confidence interval: 0.62-1.46), or pervasive developmental disorder-not otherwise specified (folic acid-adjusted risk ratio: 1.07, 95% confidence interval: 0.75-1.54; multivitamin: adjusted risk ratio: 0.87, 95% confidence interval: 0.65-1.17) compared with women reporting no supplement use in the same period.
  
  
  
  We did not find any evidence to corroborate previous reports of a reduced risk for autism spectrum disorders in offspring of women using folic acid supplements in early pregnancy.
authors.affiliation: UCLA Fielding School of Public Health, University of California, Los Angeles, USA jasvirk@ucla.edu.
authors.forename: Jasveer
authors.initials: J
authors.lastname: Virk
authors.affiliation: UCLA Fielding School of Public Health, University of California, Los Angeles, USA.
authors.forename: Zeyan
authors.initials: Z
authors.lastname: Liew
authors.affiliation: Aarhus University, Denmark.
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Odense University Hospital, Denmark.
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Nohr
authors.affiliation: University of Pittsburgh, USA.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Catov
authors.affiliation: UCLA Fielding School of Public Health, University of California, Los Angeles, USA.
authors.forename: Beate
authors.initials: B
authors.lastname: Ritz
mesh_terms: D000328:Adult; D000067877:Autism Spectrum Disorder / Q000517:prevention & control*; D003718:Denmark; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D008137:Longitudinal Studies; D016017:Odds Ratio; D016742:Preconception Care / Q000379:methods*; D011247:Pregnancy; D011295:Prenatal Care / Q000379:methods*; D012307:Risk Factors; D014803:Vitamin B Complex / Q000008:administration & dosage; D014815:Vitamins / Q000008:administration & dosage; D055815:Young Adult
chemical_list: D014815:Vitamins; D014803:Vitamin B Complex; D005492:Folic Acid
keywords: autism spectrum disorders; environmental factors