Obesity is associated with systemic inflammation, immunological changes, increased risk of respiratory infections and chronic respiratory illness. Maternal obesity in pregnancy increases the risk of pregnancy complications, caesarean sections and adverse birth outcomes, which have in turn been associated with respiratory illness in children. To our knowledge, the possible influence of maternal obesity in pregnancy on respiratory illness in early childhood beyond the newborn period has not been explored. We examined the relationship between a high maternal body mass index (BMI) in pregnancy and lower respiratory tract infections and wheeze up to 18 months of age in the Norwegian Mother and Child Study (MoBa), a population-based cohort study that includes 100 000 pregnant women, conducted at the Norwegian Institute of Public Health. We analysed data from the first 33 192 children, born between 1999 and 2005.
In unadjusted analyses maternal obesity in pregnancy was related to both respiratory infections and wheeze in the children. In multivariable analyses, only an effect on wheeze remained. The risk of wheeze increased linearly with maternal BMI in pregnancy, and was 3.3% higher [95% CI 1.2, 5.3] for children with mothers who were obese during pregnancy, than for children of mothers with normal BMI. This effect was not mediated through obesity-related pregnancy complications, low birthweight, preterm birth or caesarean section.