Prenatal exposure to PM2.5 and its composition on child growth trajectories in the first two years: A prospective birth cohort study

The findings on the relationship between prenatal exposure to particulate matter with aerodynamic diameter ≤2.5 μm (PM_2.5) and its constituent and children's growth trajectories are inconsistent. This association's sensitive exposure time window and possible gender differences remain unclear. Our aim was to determine the association between prenatal exposure to PM_2.5 and its component and children's growth trajectories by the age of two. From 2015 to 2021, 6407 mother-infant pairs were enrolled in the study. The PM_2.5 include sulfate (SO₄^2-), nitrate (NO₃^-), ammonium (NH₄⁺), organic matter (OM), and black carbon (BC), from the ChinaHighAirPollutants (CHAP) datasets. Children were followed at birth, 1, 3, 6, 9, 12, 18, and 24 months. Population-based and individual-based methods were used to simulate child growth trajectories: slow growth, normal growth, and rapid growth. The distributed lags modeling was used to identify sensitive time windows for the effects of prenatal exposure to PM_2.5 and its components on child growth. Sex-stratified analyses estimated sex differences. Median concentrations [interquartile ranges (IQRs)] were 57.46(17.3), 10.59(3.8), 14.26(4.4), 8.69(2.8), 13.05(3.4), and 2.53(0.7) μg/m³ for PM_2.5, SO₄^2-, NO₃^-, NH₄⁺, OM, and BC, respectively. Compared with the normal growth trajectory group, exposure to PM_2.5 was significantly associated with a higher risk of rapid growth trajectory in boys (ORs with 95% CI for the entire, first trimester, and second trimester of pregnancy, respectively: 1.016[1.006,1.025], 1.007[1.002,1.011], 1.007[1.002,1.011]). Exposure to PM_2.5 was significantly associated with a higher risk of slow growth trajectory in girls (ORs with 95% CI for the entire, second trimester, and third trimester of pregnancy, respectively: 1.010 [1.001,1.018], 1.006 [1.001,1.011], 1.007 [1.002,1.012]). Prenatal PM_2.5 and its composition exposure was positively associated with BMI peak in boys (βs with 95% CI for PM_2.5, SO₄^2-, NO₃^-, NH₄⁺, OM, BC: 0.004[0.000,0.007], 0.025[0.006,0.044], 0.012[0.002,0.023], 0.022[0.004,0.039], 0.016[0.001,0.031], 0.082[0.005,0.159]), and not statistically significant in girls. We observed a more pronounced BC effect in our cohort. Prenatal exposure to PM_2.5 and its component, especially at 10-22 weeks of gestation, is associated with a higher risk of rapid growth in boys and a risk of slow growth in girls.