title: Smoking during pregnancy and risk of autism spectrum disorder in a Finnish National Birth Cohort.
abstract: BACKGROUND
  Results of previous population-based studies examining associations between smoking during pregnancy and autism spectrum disorders (ASD) are contradictory. Furthermore, there is a lack of population-based studies examining the relationship between smoking during pregnancy and the main diagnostic subtypes of ASD.
  
  
  METHODS
  We conducted a population-based nested case-control study based on the Finnish Prenatal Study of Autism (FIPS-A) among liveborn infants delivered in Finland between 1987 and 2005. Data on maternal smoking during pregnancy were available from the Finnish Medical Birth Register (FMBR) since October 1990. Data on ASD in the offspring were obtained from the Finnish Hospital Discharge Register (FHDR).
  
  
  RESULTS
  Among the three subtypes of ASD, maternal smoking during the whole pregnancy was associated with an increased risk of pervasive developmental disorder (PDD) (odds ratio 1.2, 95% confidence interval 1.0, 1.5). The increase in odds persisted after controlling for maternal age, mother's socio-economic and psychiatric status, and infant's weight for gestational age. However, smoking exposure limited to the first trimester was not associated with PDD or any of the other ASD subtypes.
  
  
  CONCLUSIONS
  Maternal smoking is related to a modest increase in risk of PDD, while no associations were observed for childhood autism and Asperger's syndrome.
authors.affiliation: Department of Biostatistics,University of Turku, Finland.
authors.forename: Phuong Lien
authors.initials: PL
authors.lastname: Tran
authors.forename: Venla
authors.initials: V
authors.lastname: Lehti
authors.forename: Katja M
authors.initials: KM
authors.lastname: Lampi
authors.forename: Hans
authors.initials: H
authors.lastname: Helenius
authors.forename: Auli
authors.initials: A
authors.lastname: Suominen
authors.forename: Mika
authors.initials: M
authors.lastname: Gissler
authors.forename: Alan S
authors.initials: AS
authors.lastname: Brown
authors.forename: Andre
authors.initials: A
authors.lastname: Sourander
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008423:Maternal Age; D008875:Middle Aged; D009035:Mothers / Q000523:psychology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000209:etiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D055815:Young Adult