Prenatal exposure to air pollution and the risk of macrosomia: Identifying windows of susceptibility

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This study explores the effects of prenatal exposure to air pollution on the risk of macrosomia and its window of susceptibility.We conducted a retrospective cohort study utilizing records of birth certificates for all full-term live newborns born in Xi'an city, China from January 1, 2015, to December 31, 2018.Weekly- and trimester-specific exposures of PM2.5, PM10, NO2, and O3 during pregnancy were calculated by inverse distance weighting (IDW) based on their residences. Cox proportional hazard model and distributed lag models (DLMs) were performed to estimate the effects of air pollution exposure during pregnancy on macrosomia risk and its window of susceptibility.In total, 318,323 full-term newborns were identified, including 24,996 (7.8%) cases of macrosomia. An IQR increase in PM2.5 exposure (45.46 μg/m3) from the 33rd until the 37th weeks of gestation was positively associated with an elevated risk of macrosomia, with the strongest effect in the 37th weeks (HR = 1.007, 95%CI: 1.002–1.013). The window of susceptibility for NO2 exposure on macrosomia risk was in the 29th–35th gestational weeks, with the strongest effect in the 34th weeks (IQR = 21.96 μg/m3, HR = 1.006, 95%CI:1.000–1.013). For prenatal exposure to O3, 5th–24th weeks of gestation was identified as susceptible windows for elevated risk of macrosomia, with the strongest associations observed in the 15th weeks (IQR = 80.53 μg/m3, HR = 1.022, 95%CI: 1.011–1.033). However, we did not observe any associations between weekly exposure of PM10 and macrosomia.Our findings imply that the windows of susceptibility to PM2.5 and NO2 exposure on macrosomia are mainly in late pregnancy, whereas the windows of susceptibility to O3 exposure are in early and middle pregnancy.