Association of Maternal Body Mass Index During Early Pregnancy With Offspring Lower Respiratory Infections: A Nationwide Cohort Study

Objective: To assess whether or to what extent maternal obesity during early pregnancy could increase the risk of offspring lower respiratory infections (LRI). Study design: This population-based cohort included 688,457 live singleton births born in Denmark between 2004 and 2016. The exposure was maternal body mass index (BMI) during early pregnancy, and the outcome was LRI in offspring. Cox regression models were used to estimate hazard ratios with their 95% confidence intervals (CI) for the association. We also performed subanalysis stratified by the LRI onset age, number of infection episodes before the age of 3, infection pathogens, infection sites, duration of hospital stay due to LRI and allergic constitution of children. Results: A total of 64,725 LRIs in offspring were identified during follow-up. Maternal overweight (BMI 25.0–29.9 kg/m 2 ), moderate or severe obesity (BMI 30.0–39.9 kg/m 2 ) and very severe obesity (BMI ≥40 kg/m 2 ) were associated with a 7% (95% CI: 5%–9%), 16% (95% CI: 14%–19%) and 21% (95% CI: 13%–28%) increased risk of LRI in offspring, respectively. Higher maternal BMI was positively associated with earlier onset age, more episodes before the age of 3, and longer hospital stay of LRI in offspring. In addition, allergic constitution of offspring significantly enhanced the effect of maternal BMI on offspring LRI (44% increased risk, 95% CI: 5%–97% for very severe obesity). Conclusions: Maternal BMI during early pregnancy might be a risk factor for offspring LRI, especially in children with allergic constitution.