Prenatal Exposure to Ambient Air Pollution and Fetal Growth Trajectories in Wuhan, China

While numerous studies have examined associations between prenatal air pollution exposure and fetal growth measures, investigations assessing longitudinal growth trajectories across multiple time points during mid-to-late pregnancy remain limited.

The aim of this study is to explore the effects of prenatal exposure to air pollution on fetal growth trajectories.

From a prospective birth cohort in Wuhan, China, recruited from 2013 to 2016, we included a total of 4283 eligible pregnant women. At 16, 24, 31, and 38 weeks of gestation, we collected ultrasound measurements, including biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW). Exposure to air pollution during pregnancy was estimated for the participants' residential addresses using a spatial interpolation method. Associations between air pollutants and fetal growth parameters across four exposure windows were examined by using multiple informant models. Group-based trajectory modeling (GBTM) combined with a multinomial logistic regression model was used to explore the effect of air pollution exposure on fetal growth trajectories.

Four trajectory groups for AC, FL, and EFW, and three trajectory groups for BPD were selected based on GBTM. Compared with the reference trajectory group, exposure to higher PM_2.5 during weeks 1-16 was significantly associated with lower odds of being in the "fast growth group" for AC (OR = 0.68, 95% CI: 0.55, 0.84) and EFW (OR = 0.71, 95% CI: 0.56, 0.91). Exposures to PM_2.5, PM₁₀, NO₂, SO₂, and CO during 1-16 weeks were negatively associated with AC, FL, and EFW at 16 weeks as well as BPD, FL, and EFW at 24 weeks. Similar negative associations were observed between air pollution exposure during 25-38 weeks and AC and EFW at 38 weeks.

Our study provided evidence of negative associations between air pollution exposure during 1-16 weeks of gestation and the fast growth trajectory group. In addition, we observed distinct lagged associations between air pollution and fetal growth, with early pregnancy exposure negatively related to early and midgestational growth, and mid-to-late pregnancy exposure negatively related to growth in the late window. These results underscore the importance of identifying critical windows of susceptibility during pregnancy and support early intervention strategies to mitigate adverse fetal developmental outcomes.