title: Fetal Growth and Childhood Lung Function in the Swedish Twin Study on Prediction and Prevention of Asthma.
abstract: BACKGROUND
  Associations between fetal growth restriction and lung function impairment could be due to gestational age as well as shared (familial) genetic and environmental factors.
  
  
  OBJECTIVE
  To study the association between fetal growth and lung function in childhood while taking gestational age and familial factors into account.
  
  
  METHODS
  First, full-cohort analyses of twins were performed to study the association between birth weight, gestational age, fetal growth, and lung function (FEV1, FVC, and FEV1/FVC) in z-scores before (n = 520) and after (n = 539) bronchodilator treatment. Second, to control for gestational age and familial factors, within-twin-pair analyses were performed.
  
  
  RESULTS
  Regarding full-cohort post-bronchodilator treatment, FEV1was significantly associated with a decrease in birth weight (-0.16 z-score per 500 g; 95% confidence interval [CI], -0.28 to -0.04) and fetal growth (-0.15 z-score per 1 SD decrease; 95% CI, -0.26 to -0.04), and similar and significant associations for FVC with birth weight and fetal growth were also seen. Nonsignificant associations for FEV1and FVC with gestational age were found. The direction of effect was similar in pre-bronchodilator analyses, although with somewhat less strong and nonsignificant effect estimates for both FEV1and FVC with fetal growth. No associations were found between any of the exposure variables and FEV1/FVC either pre- or post-bronchodilator. In the within-twin-pair analyses, the direction of effect appeared similar to that of the whole cohort, but the CIs were wider.
  
  
  CONCLUSIONS
  Our results suggest that there is a significant association between restricted fetal growth and post-bronchodilator FEV1and FVC, but not FEV1/FVC, in childhood that may be independent of gestational age and shared familial factors.
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Örtqvist
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.
authors.forename: Vilhelmina
authors.initials: V
authors.lastname: Ullemar
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lundholm
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kuja-Halkola
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.
authors.forename: Patrik K E
authors.initials: PKE
authors.lastname: Magnusson
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: 2 Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.|3 Sachs' Children and Youth Hospital, Södersjukhuset, Stockholm, Sweden; and.
authors.forename: Jenny
authors.initials: J
authors.lastname: Hallberg
authors.affiliation: 1 Department of Medical Epidemiology and Biostatistics and.|4 Unit of Pediatric Allergy and Pulmonology, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Catarina
authors.initials: C
authors.lastname: Almqvist
mesh_terms: D001249:Asthma / Q000503:physiopathology / Q000517:prevention & control*; D002675:Child, Preschool; D047109:Fetal Development / Q000502:physiology*; D005544:Forecasting; D006801:Humans; D008168:Lung / Q000502:physiology*; D012129:Respiratory Function Tests; D013548:Sweden
keywords: asthma; bronchodilator; confounding; spirometry; twins