Prenatal Exposure to Size-Fractionated Particulate Matter and Fetal Growth Trajectories: Mediation by Maternal Glucose Metabolism in a Birth Cohort

The metabolic mechanisms linking prenatal particulate matter (PM) to fetal growth remain unclear. A prospective cohort of 616 mother–fetus pairs in Guangzhou had ultrasound-based fetal growth parameters repeatedly measured from mid to late pregnancy. Fetal head circumference (HC), abdominal circumference (AC), femur length (FL), and biparietal diameter (BPD) were standardized as z-scores. Estimated fetal weight (EFW) trajectories were classified as average, slow, and rapid growth. Residential PM1, PM2.5, and PM10 were assessed with 1 km spatiotemporal models. Multinomial logistic regression analyzed PM-EFW trajectory associations. Generalized estimating equations evaluated PM–fetal growth z-score relationships. Maternal plasma glucose and insulin levels at mid-pregnancy were examined as intermediate factors. Each 5 μg/m3 increase in PM was associated with higher odds of rapid EFW growth versus average growth (OR PM1 = 1.56, 95% CI: 1.03, 2.37; OR PM2.5 = 1.44, 95% CI: 1.10, 1.88; OR PM10 = 1.28, 95% CI: 1.05, 1.56). Positive associations were also observed for BPD, HC, and AC z-scores, with PM1 showing the numerically larger effect estimates. Maternal fasting plasma glucose and insulin resistance may partly explain the observed associations of PM exposure with rapid EFW growth and fetal growth parameters, with estimated proportions of 5.0–29.4%. This study highlights the potential risk of accelerated fetal growth associated with maternal PM exposures, and maternal glucose metabolism may represent a plausible pathway.