The associations of prenatal exposure to PM2.5 and its constituents with fetal growth: A prospective birth cohort in Beijing, China

Background: Limited studies investigated the association of prenatal exposure to PM2.5 and fetal growth measured by ultrasound with inconsistent results. No study evaluated the effect of PM2.5 constituents on fetal growth in utero. We aimed to investigated whether prenatal exposure to PM2.5 and its constituents was associated with fetal growth measured by ultrasound. Methods: A total of 4319 eligible pregnant women in Peking University Birth Cohort in Tongzhou (PKUBC-T) were included in the study. Based on mothers' residential addresses, we estimated prenatal PM2.5 concentrations with a satellite-based spatiotemporal model and PM2.5 constituents concentrations with a modified Community Multiscale Air Quality model. Fetal growth parameters of abdominal circumference (AC), head circumference (HC), and femur length (FL) were measured by ultrasound and then estimated fetal weight (EFW) was calculated. We calculated sex and gestational age-specific fetal growth Z-score and then defined the corresponding fetal undergrowth. Generalized estimating equation was used to investigate the association of PM2.5 and its constituents with fetal growth Z-score and fetal undergrowth. Results: Prenatal exposure to PM2.5, OC, EC, SO42-, NH4+, or NO3- was consistently associated with decreased Z-scores of fetal growth parameters (AC, HC, FL, EFW). One IQR increase of PM2.5, OC, EC, SO42-, NH4+, or NO3- was associated with -0.183 [95% confident interval (CI): -0.225, -0.141], -0.144 (95%CI: -0.181, -0.107), -0.123 (95%CI: -0.160, -0.085), -0.035 (95%CI: -0.055, -0.015), -0.095 (95%CI: -0.126, -0.064), and -0.124 (95%CI: -0.159, -0.088) decrease in EFW Z-score, respectively. Prenatal exposure to PM2.5, OC, EC, SO42-, NH4+, or NO3- was also associated with higher risk of fetal AC, HC, FL or EFW undergrowth. Conclusion: The study identified that prenatal exposure to PM2.5 or its constituents was associated with impaired fetal growth. The findings provided evidence that control measures for PM2.5 constituents should be implemented for further promoting fetal growth.