title: Gestational age, birth weight, and risk of respiratory hospital admission in childhood.
abstract: OBJECTIVE
  To investigate the risk of emergency respiratory hospital admission during childhood associated with gestational age at birth and growth restriction in utero.
  
  
  METHODS
  The study included a total population electronic birth cohort with anonymized record-linkage of multiple health and administrative data sets. Participants were 318,613 children born in Wales, United Kingdom, between May 1, 1998, and December 31, 2008. The main outcome measure was emergency respiratory hospital admissions.
  
  
  RESULTS
  The rate of admission in the first year of life ranged from 41.5 per 100 child-years for infants born before 33 weeks' gestation to 9.8 per 100 child-years for infants born at 40 to 42 weeks' gestation. The risk of any emergency respiratory admission up to age 5 years increased as gestational age decreased to <40 weeks. Even at 39 weeks' gestation, there was an increased risk of emergency hospital admissions for respiratory conditions compared with infants born at 40 to 42 weeks (adjusted hazard ratio 1.10; 95% confidence interval 1.08-1.13). Small for gestational age (<10th centile for gestation and gender-specific birth weight) was independently associated with an increased risk of any emergency respiratory admission to hospital (adjusted hazard ratio 1.07; 95% confidence interval 1.04-1.10).
  
  
  CONCLUSIONS
  The risk of emergency respiratory admission up to age 5 years decreased with each successive week in gestation up to 40 to 42 weeks. Although the magnitude of increased risk associated with moderate and late preterm births is small, the number of infants affected is large and therefore presents a significant impact on health care services.
authors.affiliation: Institute of Primary Care and Public Health, School of Medicine, Cardiff University, 5th Floor Neuadd Meirionnydd, Heath Park, Cardiff CF14 4YS, United Kingdom. ParanjothyS@cardiff.ac.uk.
authors.forename: Shantini
authors.initials: S
authors.lastname: Paranjothy
authors.forename: Frank
authors.initials: F
authors.lastname: Dunstan
authors.forename: William J
authors.initials: WJ
authors.lastname: Watkins
authors.forename: Melanie
authors.initials: M
authors.lastname: Hyatt
authors.forename: Joanne C
authors.initials: JC
authors.lastname: Demmler
authors.forename: Ronan A
authors.initials: RA
authors.lastname: Lyons
authors.forename: David
authors.initials: D
authors.lastname: Fone
mesh_terms: D001249:Asthma / Q000453:epidemiology / Q000209:etiology* / Q000628:therapy; D001724:Birth Weight; D002675:Child, Preschool; D015331:Cohort Studies; D004630:Emergencies; D005260:Female; D005865:Gestational Age; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D008297:Male; D012042:Registries; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000209:etiology* / Q000628:therapy; D012307:Risk Factors; D014852:Wales / Q000453:epidemiology
keywords: birth weight; emergency hospital admission; gestation; respiratory disease