Beyond household and individual factors: examining the association between ambient air pollution and birth outcomes in India.

Low birth weight (LBW) and preterm birth (PTB) are primary factors contributing to morbidity and mortality among children aged under 5, resulting in a range of short- and long-term health consequences worldwide. Among the various risk factors, ambient air pollution poses a significant environmental risk and is a key determinant of child health. The prevalence of LBW and PTB among under 5 children sampled from the NFHS-5, 2019-2021, was combined with monthly PM_2.5 data (2013-2021) obtained from the Atmospheric Composition Analysis Group at Washington University. Multivariable logistic regression models were used, and a stratified analysis was applied to understand the potential effect modifiers in LBW and PTB. Further, the geographical variation of LBW and PTB spatial autocorrelation (Moran's I) was used. Geographically weighted regression and ordinary least square spatial regression were used to identify the spatial heterogeneity associated with selected variables. The study comprises a total of 208,181 under 5 children. Out of these children, the LBW rate was 17.41%, and the rate of PTB was 12.42%. The in-utero exposure to the mean concentration of PM_2.5 was 56.01 μg/m³. The odds of suffering from LBW showed a non-linear shift when PM_2.5 levels rose from the first octile (<28.02 μg/m³) to the last octile (>93.84 μg/m³) (adjusted odds ratio (AOR): 1.06, 95% CI: 1.01-1.12). While comparing the first octile of exposure to PM_2.5 (>93.84 μg/m³) to the last octile, there was a 52% more likelihood of having PTB (AOR: 1.52, 95% CI: 1.43-1.61) after accounting for all relevant factors. These findings highlight the urgent need for a thorough strategy to control the air quality in India. Further, to reduce adverse birth outcomes, longitudinal studies and other co-pollutants can consider assessing the possible mechanisms mediating the relationship between maternal exposure and ambient air pollution.