Exposure to ${\mathrm{PM}}_{2.5}$ during Pregnancy and Fetal Growth in Eastern Massachusetts, USA

Background: Prior studies have examined the association between fine particulate matter [PM $\le 2.5\mu m$ in aerodynamic diameter (${\mathrm{PM}}_{2.5}$)] and fetal growth with either limited spatial or temporal resolution.

Objectives: In this study, we examined the association between ${\mathrm{PM}}_{2.5}$ exposure during pregnancy and fetal growth measures (ultrasound parameters and birth weight) in a pregnancy cohort using spatiotemporally resolved ${\mathrm{PM}}_{2.5}$ in Eastern Massachusetts, USA.

Methods: We used ultrasound measures of biparietal diameter (BPD), head circumference, femur length, and abdominal circumference (AC), in addition to birth weight, from 9,446 pregnancies that were delivered at the Beth Israel Deaconess Medical Center from 2011-2016. We used linear mixed-effects models to examine the associations of ${\mathrm{PM}}_{2.5}$ in two exposure windows (the first 16 wk of pregnancy and the cumulative exposure up until the assessment of fetal growth) with anatomic scans (ultrasound $\text{measures at}<24\mathrm{wk}$), growth scans (ultrasound $\text{measures at}\ge 24\mathrm{wk}$), and birth weight. All models were adjusted for sociodemographic characteristics, long-term trends, and temperature.

Results: Higher ${\mathrm{PM}}_{2.5}$ exposure in the first 16 wk was associated with smaller fetal growth measures, where associations were particularly strong for BPD, AC, and birth weight. For example, a $5\text{-}{\mu g/m}^3$ increase in ${\mathrm{PM}}_{2.5}$ was associated with a lower mean BPD $z$-score of $-0.19$ (95% CI: $-0.31$, $-0.06$) before 24 wk, a lower mean AC $z$-score of $-0.15$ (95% CI: $-0.28$, $-0.01$) after 24 wk, and a lower mean birth weight $z$-score of $-0.11$ (95% CI: $-0.20$, $-0.01$). Analyses examining the associations with cumulative ${\mathrm{PM}}_{2.5}$ exposure up until the assessment of fetal growth produced attenuated associations.

Conclusions: Higher gestational exposure to ${\mathrm{PM}}_{2.5}$ was associated with smaller fetal growth measures at levels below the current national standards. https://doi.org/10.1289/EHP9824.