Objective: The aim of this study was to investigate the association between maternal overweight before pregnancy and offspring asthma in an ongoing birth cohort study. Maternal overweight may affect the pulmonary and immunological development of the fetus in utero because of the increased levels of inflammatory factors associated with being overweight and thereby increase the asthma risk in childhood.
Design: Birth cohort study with follow-up until 8 years of age.
Subjects: The study population included 3963 children and their mothers who participated in the Prevention and Incidence of Asthma and Mite Allergy study.
Measurements: Maternal overweight before pregnancy was defined as a body mass index (BMI) above 25 kg m(-2). Data on wheeze, dyspnea and prescription of inhaled corticosteroids of the child were reported yearly by the parents in a questionnaire. Sensitization to inhalant allergens and bronchial hyperresponsiveness (BHR) were determined at 8 years. Effect modification by predisposition for asthma in the child was tested. Data were analyzed by logistic regression and generalized estimating equations analyses.
Results: At 8 years, 14.4% (n=571) of the children had asthma. In total, 20.9% (n=830) of the mothers were overweight before pregnancy. In children predisposed for asthma (n=1058), maternal overweight before pregnancy was associated with an increased risk of asthma in the child at 8 years (OR=1.52, 95% CI: 1.05-2.18) after adjustment for confounding factors, birth weight and the child's BMI. No association was observed in children without a predisposition (OR=0.86, 95% CI: 0.60-1.23). There was no association with sensitization or BHR.
Conclusion: Children with a predisposition for asthma may have a higher risk to develop asthma during childhood when their mothers are overweight before pregnancy, irrespective of the child's BMI.