Birth weight for gestational age and the risk of asthma in childhood and adolescence: a retrospective cohort study
Carter, Jillian Hansen
Woolcott, Christy Gwen
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Objective: To examine the association between birthweight for gestational age and asthma in childhood and adolescence while controlling for potential confounders and considering smoking as an effect modifier. Methods: A retrospective cohort of all singleton term births in Nova Scotia, Canada between 1989 and 1993 was identified in the provincial perinatal database and followed through 2014 by linking with administrative health data. The outcome, asthma, was defined as having one hospitalization or two physician visits with an ICD code for asthma in a 2-year period. Birthweight was categorized as small (SGA), large (LGA), or appropriate (AGA) for gestational age. Multivariable-adjusted Cox proportional hazards models were used to examine the association between the birthweight for gestational age and asthma and to test for effect modification by maternal smoking in pregnancy. Results: Of the 40,724 cohort children, 10.5% and 11.7% were born SGA and LGA, respectively, and the risk of developing asthma to age 18 years was 30.2%. The adjusted hazard ratios (HR) for SGA and LGA (relative to AGA) and asthma were 1.07 [95% CI 1.02, 1.14], and 0.96 [95% CI 0.91, 1.02], respectively. Relative to AGA children born to non-smoking mothers, SGA children were not at increased risk of asthma (HR 1.02), whereas both AGA and SGA children born to smoking mothers were at significantly increased risk (HR 1.14 and 1.29, respectively). Conclusions: Our findings suggest that SGA in term infants is not associated with asthma in childhood in the absence of smoking in pregnancy.
Carter JH, Woolcott CG, Liu L, Kuhle S. Birth weight for gestational age and the risk of asthma in childhood and adolescence: a retrospective cohort study. Arch Dis Child. 2019 Feb;104(2):179-183. http://dx.doi.org/10.1136/archdischild-2018-315059. Epub 2018 Jul 19. PMID: 30026251.