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Gestational age at birth and wheezing trajectories at 3–11 years
  1. Caroline Leps1,2,
  2. Claire Carson2,
  3. Maria A Quigley2
  1. 1 Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  2. 2 National Perinatal Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK
  1. Correspondence to Caroline Leps; caroline.leps{at}


Objective Children born preterm have an increased risk of asthma in early childhood. We examined whether this persists at 7 and 11 years, and whether wheezing trajectories across childhood are associated with preterm birth.

Design Data were from the UK Millennium Cohort Study, which recruited children at 9 months, with follow-up at 3, 5, 7 and 11 years.

Outcomes Adjusted ORs (aOR) were estimated for recent wheeze and asthma medication use for children born <32, 32–33, 34–36 and 37–38 weeks’ gestation, compared with children born at full term (39–41 weeks) at 7 (n=12 198) and 11 years (n=11 690). aORs were also calculated for having ‘early-remittent’ (wheezing at ages 3 and/or 5 years but not after), ‘late’ (wheezing at ages 7 and/or 11 years but not before) or ‘persistent/relapsing’ (wheezing at ages 3 and/or 5 and 7 and/or 11 years) wheeze.

Results Birth <32 weeks, and to a lesser extent at 32–33 weeks, were associated with an increased risk of wheeze and asthma medication use at ages 7 and 11, and all three wheezing trajectories. The aOR for ‘persistent/relapsing wheeze’ at <32 weeks was 4.30 (95% CI 2.33 to 7.91) and was 2.06 (95% CI 1.16 to 2.69) at 32–33 weeks. Birth at 34–36 weeks was not associated with asthma medication use at 7 or 11, nor late wheeze, but was associated with the other wheezing trajectories. Birth at 37–38 weeks was not associated with wheeze nor asthma medication use.

Conclusions Birth <37 weeks is a risk factor for wheezing characterised as ‘early-remittent’ or ‘persistent/relapsing’ wheeze.

  • neonatology
  • asthma < pulmonology
  • epidemiology

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  • Contributors CL carried out all statistical analyses, helped design the statistical analysis, drafted the initial manuscript and approved the final manuscript as submitted. CC and MAQ conceptualised the research question, cleaned up the Millennium Cohort Data Set, aided in statistical method design, edited the manuscript and approved the final manuscript as submitted.

  • Funding CL completed this study while on a Rhodes Scholarship.

  • Competing interests None declared.

  • Ethics approval Multi-Centre Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All data are freely available from the Millennium Cohort Study.

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