The associations of particulate matters with fetal growth in utero and birth weight: A birth cohort study in Beijing, China

Background: Previous studies examined the associations of particulate matters (PM) with fetal growth in utero or birth weight with inconsistent results, and few studies investigated that whether the associations of PM with fetal growth in utero also present at birth. We aimed to investigate the associations of PM with both fetal growth in utero and birth weight. Methods: We established a birth cohort (2014–2017) with 18,863 singleton pregnancies in Tongzhou Maternal and Child Hospital of Beijing, China. Maternal exposure to PM with aerodynamic diameters ≤2.5 μm and ≤ 10 μm (PM2.5/PM10) during pregnancy was estimated using the inverse distance weighting method. Estimated birth weight (EFW) was assessed by ultrasound measurements and birth weight was measured at birth, which were both standardized as gestational-age- and gender-adjusted Z-score. EFW undergrowth, low birth weight (LBW) and small-for-gestational-age were defined as the categorized outcomes. Generalized estimating equations and generalized linear regression were used to examine the associations of PM with quantitative and categorized outcomes, controlling for temperature, greenspace and individual covariates. Results: A 10 μg/m3 increase in PM2.5 and PM10 were associated with lower EFW Z-score [−0.031, 95% confident interval (CI): −0.047, −0.016 and −0.030, 95% CI: −0.043, −0.017]. A 10 μg/m3 increase in PM2.5 was associated with lower birth weight Z-score (−0.035, 95% CI: −0.061, −0.010) and higher risk of LBW (OR = 1.240, 95% CI: 1.019, 1.508). These results remained robust in co-pollutant models and sensitivity analyses. We didn't find significant results in other analyses. Conclusions: The study identified an inverse association between PM and fetal growth in utero. The association between PM2.5 and fetal growth persisted from pregnancy to birth. This study supported that further actions towards controlling air pollution are strongly recommended for promoting early-life health.

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