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. 2025 Dec 1;8(12):e2551459.
doi: 10.1001/jamanetworkopen.2025.51459.

Air Pollution Exposure and Birth Weight in the ECHO Cohort

Whitney Cowell  1 , Hsiao-Hsien Leon Hsu  2 , Allan C Just  3 , Itai Kloog  2 , Brent A Coull  4 , Ander Wilson  5 , Alison E Hipwell  6 , Margaret R Karagas  7 , Frank D Gilliland  8 , Amy M Padula  9 , Kecia N Carroll  2   10 , Jean M Kerver  11 , Akhgar Ghassabian  1 , Carlos A Camargo Jr  12 , Dana Dabelea  13 , Daphne Koinis-Mitchell  14 , Viren D'Sa  14 , Mehtap Haktanir Abul  15 , Joseph M Braun  3 , Lisa A Croen  16 , Tina Hartert  17 , Akihiro Shiroshita  18 , Janet L Peacock  7 , Jenae M Neiderhiser  19 , Leslie D Leve  20 , Jody M Ganiban  21 , Augusto A Litonjua  22 , Cindy T McEvoy  23 , Meredith B Haag  24 , Rebecca J Schmidt  25 , Amanda J Goodrich  25 , Kristen Lyall  26 , Heather E Volk  27 , Thomas G O'Connor  28 , David Q Rich  29 , Christine A Porucznik  30 , Rosalind J Wright  31 ; ECHO Cohort Consortium
Collaborators, Affiliations

Air Pollution Exposure and Birth Weight in the ECHO Cohort

Whitney Cowell et al. JAMA Netw Open. .

Abstract

Importance: Prior studies report negative associations between prenatal exposure to fine particulate matter (ie, aerodynamic diameter <2.5 µg; PM2.5) and birth weight, but have typically averaged exposure across pregnancy, which may not reveal windows of susceptibility.

Objective: To identify windows of prenatal susceptibility to PM2.5.

Design, setting, and participants: This was a retrospective analysis of a prospectively enrolled cohort study. Participants were enrolled at 1 of 50 sites participating in the US Environmental Influences on Child Health Outcomes Cohort. The study included full-term, singleton births occurring between September 2003 and December 2021. Statistical analyses were conducted from March 2024 to February 2025.

Exposures: Daily residential PM2.5 exposure was estimated using a machine-learning model covering the contiguous US and mean exposure estimates were calculated for each week of pregnancy.

Main outcomes and measures: Bayesian distributed lag interaction models were used to examine cumulative and week-specific associations between PM2.5 exposure and birth weight for gestational age (BWGA) z scores. Interactions with sex, race and ethnicity, and region were also examined.

Results: The sample of 16 868 mother-newborn pairs (maternal mean [SD] age, 30.4 [5.5] years; 605 [3.6%] Asian, 2197 [13.0%] Black or Black-Hispanic, 3407 [20.2%] Hispanic, 9251 [54.8%] non-Hispanic White, and 1408 [8.4%] other) included 15 806 unique mothers and 1062 mothers with 2 or more children in the study. Mean (SD) weekly PM2.5 exposure during pregnancy was relatively low, at 8.03 (2.3) µg/m3, and overall mean (SD) birth weight was 3410.7 (464.5) g. In the sample overall, there was a negative association between PM2.5 exposure and BWGA z score (β = -0.06; 95% credible interval [CrI], -0.10 to -0.03), with a critical window in early gestation (weeks 1-5) that persisted only among males (β = -0.06; 95% CrI, -0.10 to -0.02). When examining differences by region, there were negative associations in the Northeast (β = -0.09; 95% CrI, -0.15 to -0.03), Midwest (β = -0.11; 95% CrI, -0.17 to -0.05; critical window, 12-18 weeks), and South (β = -0.18; 95% CrI, -0.17 to -0.05; critical window, 3-9 weeks).

Conclusions and relevance: In this cohort study, higher PM2.5 exposure was associated with lower BWGA z score, with critical windows identified during early pregnancy to midpregnancy; however, findings varied by sex and region. Understanding windows of susceptibility to environmental exposures can help guide research on underlying biological processes and can inform strategies for limiting exposure during certain periods of pregnancy.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Coull reported receiving grants from Apple Inc outside the submitted work. Dr Braun reported receiving personal fees for serving as an expert witness on behalf of plaintiffs involved in litigation related to per- and polyfluoroalkyl substances–contaminated drinking water outside the submitted work. Dr Hartert reported receiving personal fees from American Thoracic Society, Parker B. Francis Foundation Council of Scientific Advisors, UpToDate, AAAAI, National Institutes of Health (NIH) National Heart, Lung, and Blood Institute, and Pfizer outside the submitted work. Dr Schmidt reported receiving personal fees from Linus Technology outside the submitted work. No other disclosures were reported.

Figures

Figure 1.
Figure 1.. Cumulative and Time-Varying Associations Between Weekly Prenatal Fine Particulate Matter (PM2.5) and Birth Weight For Gestational Age (BWGA) z Score
Estimates are provided per 1-µg/m3 increased PM2.5 exposure, and the model is adjusted for maternal age, education, prepregnancy body mass index, parity, tobacco use during pregnancy, ambient temperature, and US geographic region of residence. Error bar (A) and shading (B) indicate 95% credible intervals.
Figure 2.
Figure 2.. Cumulative and Time-Varying Associations Between Weekly Prenatal Fine Particulate Matter (PM2.5) and Birth Weight For Gestational Age (BWGA) z Score With an Interaction for Newborn Sex
Estimates are provided per 1-µg/m3 increased PM2.5 exposure, and the model is adjusted for maternal age, education, prepregnancy body mass index, parity, tobacco use during pregnancy, ambient temperature, and US geographic region of residence. Error bars (A) and shading (B) indicate 95% credible intervals.
Figure 3.
Figure 3.. Cumulative and Time-Varying Associations Between Weekly Prenatal Fine Particulate Matter (PM2.5) and Birth Weight for Gestational Age (BWGA) z Score With an Interaction for Maternal Self-Identified Race and Ethnicity
Estimates are provided per 1-µg/m3 increased PM2.5 exposure, and the model is adjusted for maternal age, education, prepregnancy body mass index, parity, tobacco use during pregnancy, ambient temperature, newborn sex, and US geographic region of residence. Other was defined as American Indian or Alaska Native, Native Hawaiian or Other Pacific Islander, or more than 1 race. Error bars (A) and shading (B) indicate 95% credible intervals.
Figure 4.
Figure 4.. Cumulative and Time-Varying Associations Between Weekly Prenatal Fine Particulate Matter (PM2.5) and Birth Weight for Gestational Age (BWGA) z Score With an Interaction for US Geographic Region
Estimates are provided per 1-µg/m3 increased PM2.5 exposure, and the model is adjusted for maternal age, education, prepregnancy body mass index, parity, tobacco use during pregnancy, ambient temperature, and newborn sex. Error bars (A) and shading (B) indicate 95% credible intervals.
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