title: Respiratory symptoms in the first 7 years of life and birth weight at term: the PIAMA Birth Cohort.
abstract: BACKGROUND
  The relation between birth weight and respiratory symptoms and asthma in children remains unclear. Previous studies focused on a relation at separate ages. A longitudinal analysis may lead to a better understanding.
  
  
  OBJECTIVE
  To estimate the effect of birth weight on the development and course of respiratory symptoms and asthma in the first 7 years of life.
  
  
  METHODS
  In a prospective birth cohort study, 3,628 children with a gestational age 37 weeks or more were monitored for 7 years. Parental questionnaires were used to assess respiratory health yearly. Associations of birth weight with respiratory symptoms (wheezing, coughing, respiratory infections) and doctor's diagnosis of asthma were assessed in a repeated-event analysis.
  
  
  RESULTS
  Lower birth weight was associated with more respiratory symptoms (odds ratio [OR] per kg decrease in birth weight, 1.21; 95% confidence interval [CI], 1.09-1.34). The effect of birth weight increased from age 1 to 5, but decreased thereafter and was no longer significant at the age of 7. The effect of birth weight on respiratory symptoms was significantly greater among children exposed to tobacco smoke in their home than among nonexposed children (OR at 5 yr: 1.21 [95% CI, 1.02-1.44] and 1.52 [95% CI, 1.23-1.87], respectively). Birth weight and a doctor's diagnosis of asthma were not related (OR, 1.06; 95% CI, 0.82-1.37).
  
  
  CONCLUSIONS
  A lower birth weight in children born at term is associated with a transiently increased risk of respiratory symptoms. This effect is enhanced by environmental tobacco smoke exposure.
authors.affiliation: Department of Pediatrics/Respiratory Medicine, Erasmus University, 3000 CB Rotterdam, The Netherlands.
authors.forename: Daan
authors.initials: D
authors.lastname: Caudri
authors.forename: Alet
authors.initials: A
authors.lastname: Wijga
authors.forename: Ulrike
authors.initials: U
authors.lastname: Gehring
authors.forename: Henriette A
authors.initials: HA
authors.lastname: Smit
authors.forename: Bert
authors.initials: B
authors.lastname: Brunekreef
authors.forename: Marjan
authors.initials: M
authors.lastname: Kerkhof
authors.forename: Maarten
authors.initials: M
authors.lastname: Hoekstra
authors.forename: Jorrit
authors.initials: J
authors.lastname: Gerritsen
authors.forename: Johan C
authors.initials: JC
authors.lastname: de Jongste
mesh_terms: D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology*; D001724:Birth Weight; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis; D066298:In Vitro Techniques; D015994:Incidence; D007223:Infant; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D011247:Pregnancy; D012120:Respiration Disorders / Q000175:diagnosis / Q000453:epidemiology*; D012737:Sex Factors; D014028:Tobacco Smoke Pollution
chemical_list: D014028:Tobacco Smoke Pollution