Maternal obesity in pregnancy and respiratory health in early childhood

Abstract

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.

Figure 1

Path-model for investigating direct and indirect effects of maternal prepregnancy BMI on childhood respiratory health.

Figure 2

The adjusted relationship between maternal BMI in pregnancy and wheezing in children up to 18 months of age for 33 192 children in the Norwegian Mother and Child cohort study born 1999 - 2005. Adjusted for complications in pregnancy, low birthweight, preterm birth, caesarean section, sex, plural births, and maternal characteristics (asthma, age, income, education, marital status, smoking in pregnancy, parity), and breast feeding, postnatal smoking and type of day care. Dashed lines show the 95% confidence interval. The rug on the x-axis shows the individual data points. The y-scale shows risk difference for wheeze with value zero set arbitrary in the middle of the scale.