Impaired Fetal Growth Decreases the Risk of Childhood Atopic Eczema: A Swedish Twin Study
PURPOSE OF THE STUDY.
Previous studies have revealed an association between high birth weight and gestational age and increased risk for subsequent atopic eczema. These researchers sought to evaluate associations between fetal growth and risk of atopic eczema or allergic rhinitis in a prospective twin cohort.
Data were collected via telephone interviews between October 2004 and July 2007 from parents participating in the Swedish Twin and Medical Birth registers. Children were 9 or 12 years old. The study base included 11 020 twins; data were available for atopic eczema among 10 132 and for allergic rhinitis among 10 896 participants.
Birth weight, gestational age, birth weight by gestational week, and gender in SD score, as a measure of fetal growth, and birth length were used as exposure variables. Exposure variables were handled as both categorized and continuous variables. To control for shared genetic and environmental factors, co-twin–control analyses were performed in twin pairs discordant for atopic eczema or allergic rhinitis.
The rate of atopic eczema increased with birth weight from 12.6% in twin children born at <2000 g to 17.3% in children born at ≥3500 g. The overall rate of allergic rhinitis was 8.4%, and there was no clear relationship with birth weight, gestational age, or birth length. In the cohort analyses, the odds ratio for atopic eczema was 1.62 for a 500-g increase in birth weight. The odds ratio for allergic rhinitis was 1.00 for a 500-g increase in birth weight. The co-twin–control analysis on atopic eczema resulted in an odds ratio of 3.93 for a 500-g increase in birth weight, and there was no significant difference between monozygotic and dizygotic twins. The co-twin–control analysis revealed no evidence of association between allergic rhinitis and weight.
The risk of childhood atopic eczema increased with increasing birth weight. In the co-twin–control analysis, odds ratios did not decrease, and odds ratios did not differ between monozygotic and dizygotic twins, which indicates that genetic or shared environmental factors do not explain this association. The study results indicate that fetal growth influences the risk of childhood atopic eczema but not allergic rhinitis.
It is not surprising that maternal and fetal characteristics influence the development of childhood disease. In addition to fetal growth associations, the authors provided extensive descriptive data for the rates of atopic eczema and allergic rhinitis by all queried child and maternal characteristics. Additional studies of singletons are necessary to further evaluate the reasons for the association of fetal growth and atopic disease.
- Copyright © 2011 by the American Academy of Pediatrics