Pregnancy Trimester-Specific Exposure to Ambient Air Pollution and Child Respiratory Health Outcomes in the First 2 Years of Life: Effect Modification by Maternal Pre-Pregnancy BMI

Prenatal exposure to air pollution is associated with childhood respiratory health; however, no previous studies have examined maternal pre-pregnancy body mass index (BMI) as a potential effect modifier. We investigated whether maternal pre-pregnancy BMI modified the association of trimester-specific air pollution divided into quartiles of exposure (Q1–4) on respiratory health in the Growing Up in Singapore towards healthy Outcomes (GUSTO) study ( n = 953) in 2-year-old children. For episodes of wheezing, children of overweight/obese mothers and who were exposed to particulate matter less than 2.5 μm (PM 2.5 ) in the first trimester had an adjusted incidence rate ratio (IRR) (95% confidence interval (CI)) of 1.85 (1.23–2.78), 1.76 (1.08–2.85) and 1.90 (1.10–3.27) in quartile (Q) 2–4, with reference to Q1. This association is seen in the second trimester for bronchiolitis/bronchitis. The risk of ear infection in the first year of life was associated with exposure to PM 2.5 in the first trimester with adjusted Odds Ratio (adjOR) (95% CI) = 7.64 (1.18–49.37), 11.37 (1.47–87.97) and 8.26 (1.13–60.29) for Q2–4, and similarly in the second year with adjOR (95% CI) = 3.28 (1.00–10.73) and 4.15 (1.05–16.36) for Q2–3. Prenatal exposure to air pollution has an enhanced impact on childhood respiratory health, and differs according to maternal pre-pregnancy BMI.