title: Prenatal and perinatal risk factors in a twin study of autism spectrum disorders.
abstract: BACKGROUND
  Multiple studies associate prenatal and perinatal complications with increased risks for autism spectrum disorders (ASDs). The objectives of this study were to utilize a twin study design to 1) Investigate whether shared gestational and perinatal factors increase concordance for ASDs in twins, 2) Determine whether individual neonatal factors are associated with the presence of ASDs in twins, and 3) Explore whether associated factors may influence males and females differently.
  
  
  METHODS
  Data from medical records and parent response questionnaires from 194 twin pairs, in which at least one twin had an ASD, were analyzed.
  
  
  RESULTS
  Shared factors including parental age, prenatal use of medications, uterine bleeding, and prematurity did not increase concordance risks for ASDs in twins. Among the individual factors, respiratory distress demonstrated the strongest association with increased risk for ASDs in the group as a whole (OR 2.11, 95% CI 1.27-3.51). Furthermore, respiratory distress (OR 2.29, 95% CI 1.12-4.67) and other markers of hypoxia (OR 1.99, 95% CI 1.04-3.80) were associated with increased risks for ASDs in males, while jaundice was associated with an increased risk for ASDs in females (OR 2.94, 95% CI 1.28-6.74).
  
  
  CONCLUSIONS
  Perinatal factors associated with respiratory distress and other markers of hypoxia appear to increase risk for autism in a subgroup of twins. Future studies examining potential gender differences and additional prenatal, perinatal and postnatal environmental factors are required for elucidating the etiology of ASDs and suggesting new methods for treatment and prevention.
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA. Electronic address: wendyf@stanford.edu.
authors.forename: Wendy
authors.initials: W
authors.lastname: Froehlich-Santino
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Amalia
authors.initials: A
authors.lastname: Londono Tobon
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Sue
authors.initials: S
authors.lastname: Cleveland
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Torres
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Phillips
authors.affiliation: Autism Genetic Resource Exchange, Autism Speaks, Los Angeles, CA, USA.
authors.forename: Brianne
authors.initials: B
authors.lastname: Cohen
authors.affiliation: Autism Genetic Resource Exchange, Autism Speaks, Los Angeles, CA, USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Torigoe
authors.affiliation: Autism Genetic Resource Exchange, Autism Speaks, Los Angeles, CA, USA.
authors.forename: Janet
authors.initials: J
authors.lastname: Miller
authors.affiliation: Autism Genetic Resource Exchange, Autism Speaks, Los Angeles, CA, USA.
authors.forename: Angie
authors.initials: A
authors.lastname: Fedele
authors.affiliation: Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Collins
authors.affiliation: Impact Assessment, Inc, La Jolla, CA, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Smith
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Linda
authors.initials: L
authors.lastname: Lotspeich
authors.affiliation: Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Croen
authors.affiliation: University of California, Davis, MIND Institute, Sacramento, CA, USA.
authors.forename: Sally
authors.initials: S
authors.lastname: Ozonoff
authors.affiliation: Autism Genetic Resource Exchange, Autism Speaks, Los Angeles, CA, USA.
authors.forename: Clara
authors.initials: C
authors.lastname: Lajonchere
authors.affiliation: Environmental Health Investigations Branch, California Department of Public Health, Richmond, CA, USA.
authors.forename: Judith K
authors.initials: JK
authors.lastname: Grether
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Ruth
authors.initials: R
authors.lastname: O'Hara
authors.affiliation: Department of Psychiatry, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Joachim
authors.initials: J
authors.lastname: Hallmayer
mesh_terms: D000367:Age Factors; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology* / Q000235:genetics*; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D005865:Gestational Age; D006801:Humans; D008297:Male; D010290:Parents; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000503:physiopathology*; D011446:Prospective Studies; D012307:Risk Factors; D018709:Statistics, Nonparametric
keywords: Autism; Environment; Perinatal; Pregnancy complications; Prenatal; Twins
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