Maternal body mass index: Relation with infant respiratory symptoms and infections

Background: Maternal obesity is increasingly prevalent in many westernized countries. Many studies report associations between maternal obesity and childhood wheeze or asthma but few have considered maternal obesity in relation to respiratory infections or symptoms other than wheeze during infancy. This study assesses the relationship between maternal BMI and reported wheeze, cough and respiratory infections during the first year of life. Methods: In 2799 mother-child pairs, we examined the relations between maternal pre-pregnancy BMI and pregnancy weight gain and reported offspring wheeze, prolonged cough, lower respiratory tract infection, croup, and ear infection before age 1 year, along with reported diarrhea or vomiting. Maternally reported paternal BMI was included in the models as a proxy for unmeasured confounding by shared familial factors. Results: Higher maternal BMI was associated with increased risks of offspring wheeze, prolonged cough and lower respiratory tract infection (relative risks (95%CI) per 5 kg/m² 1.09 (1.05-1.13), 1.09 (1.03-1.14), and 1.13 (1.07-1.20), respectively). These associations remained after adjusting for maternally reported paternal BMI. No associations were found with croup, ear infection, or diarrhea or vomiting. Pregnancy weight gain was not associated with any of the offspring symptoms or illnesses. Discussion: Higher maternal BMI is associated with increased risk of wheeze, cough, and maternally reported lower respiratory tract infection in infancy. These associations were independent of maternally reported paternal BMI. These observations might be explained by intrauterine effects of maternal obesity upon respiratory or immune development.