Birth weight, gestational age, fetal growth and childhood asthma hospitalization
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ALLERGY, ASTHMA & CLINICAL IMMUNOLOGY
RESEARCH
Open Access
Birth weight, gestational age, fetal growth and childhood asthma hospitalization Xiaoqin Liu1,2*, Jørn Olsen1,3, Esben Agerbo4,5, Wei Yuan2, Sven Cnattingius6, Mika Gissler7,8 and Jiong Li1
Abstract Background: Childhood asthma may have a fetal origin through fetal growth and development of the immunocompetence or respiratory organs. Objective: We examined to which extent short gestational age, low birth weight and fetal growth restriction were associated with an increased risk of asthma hospitalization in childhood. Methods: We undertook a cohort study based on several national registers in Denmark, Sweden and Finland. We included all live singleton born children in Denmark during 1979-2005 (N = 1,538,093), in Sweden during 1973-2004 (N = 3,067,670), and a 90% random sample of singleton children born in Finland during 1987-2004 (N = 1,050,744). The children were followed from three years of age to first hospitalization for asthma, emigration, death, their 18th birthday, or the end of study (the end of 2008 in Denmark, and the end of 2007 in Sweden or Finland), whichever came first. We computed the pseudo-values for each observation and used them in a generalized estimating equation to estimate relative risks (RR) for asthma hospitalization. Results: A total of 131,783 children were hospitalized for asthma during follow-up. The risk for asthma hospitalization consistently increased with lower birth weight and shorter gestational age. A 1000-g decrease in birth weight corresponded to a RR of 1.17 (95% confidence interval (CI) 1.15-1.18). A one-week decrease in gestational age corresponded to a RR of 1.05 (95% CI 1.04-1.06). Small for gestational age was associated with an increased risk of asthma hospitalization in term but not in preterm born children. Conclusions: Fetal growth and gestational age may play a direct or indirect causal role in the development of childhood asthma. Keywords: Asthma, Birth weight, Gestational age, Hospitalization, Small for gestational age
Introduction Asthma is a significant health problem for families and society [1]. More than 50% of children with asthma develop symptoms before their fifth birthday [2], indicating that pre- or perinatal factors may play a causal role. Preterm birth, low birth weight and fetal growth restriction may be associated with disturbed immunocompetence and restrict normal lung growth and development [3-6], thereby predispose children to asthma later in life * Correspondence: [email protected] 1 Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark 2 Department of Epidemiology and Social Science on Reproductive Health, Shanghai Institute of Planned Parenthood Research, WHO Collaborating Center for Research in Human Reproduction, National Population & Family Planning Key Laboratory of Contraceptive Drugs and Devices, Shanghai, China Full list of author information is available at the end of the article
[4,7]. However, epidemiologic findings linking gestational age,
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