Abstract
This study investigated trimester-specific associations between maternal exposure to fine particulate matter (PM(2.5)) chemical constituents, precursor gases, and low birth weight (LBW) risk. Using a retrospective cohort of 4,855 singleton live births in Beijing (2017–2018), the study assessed exposure to 8 PM(2.5) components and 4 precursor gases across pregnancy stages via logistic regression and quantile g-computation for mixture effects. The LBW prevalence was 3.7%. Third-trimester exposure to PM(2.5)-bound nitrate (adjusted odds ratio [aOR] = 2.3, 95% CI: 1.4–3.4) and NO(2) (aOR = 3.5, 95% CI: 1.9–6.7) showed strongest associations with LBW. Whole-pregnancy exposure to magnesium (aOR = 2.4, 95% CI: 1.2–4.4) and O(3) (aOR = 2.0, 95% CI: 1.4–2.8) also demonstrated significant risks. Mixture analysis identified potassium and calcium as the strongest positive PM(2.5) contributors to LBW risk, while HNO(2) and NO(2) dominated precursor gas impacts. These findings emphasize that chemical composition should be explicitly considered in air pollution studies to achieve a comprehensive assessment of health effects. Targeting pollution sources characterized by nitrate-rich combustion products and traffic-related emissions, especially during late pregnancy, could yield substantial public health benefits by reducing LBW incidence. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12884-026-08788-w.