Association between outdoor PM2.5 exposure during pregnancy and preterm birth in Bangladesh using demographic and health survey data 2022

Bangladesh consistently ranks among the countries with the highest fine particulate matter (PM2.5) pollution levels globally, yet evidence on the association between PM2.5 exposure during pregnancy and preterm birth (PTB) remains limited. Therefore, we assessed the association between outdoor PM2.5 exposure and PTB across different periods of pregnancy. We used data from the Bangladesh Demographic and Health Survey (BDHS) to conduct this cross-sectional study. The final analytical sample comprised 8,059 births occurring between 2017 and 2022, along with corresponding sociodemographic, healthcare access and reproductive characteristics. Monthly outdoor PM2.5 concentrations were estimated using satellite-based models and linked to each survey cluster. Multivariable logistic regression was used to estimate the association between PM2.5 exposure and PTB across progressively adjusted models. The mean monthly PM2.5 concentration was 67.9 µg/m3 during the study period. In the fully adjusted model, each 10 µg/m3 increase in complete-pregnancy PM2.5 exposure was associated with 16% higher odds of PTB (OR = 1.16, 95% CI: 1.06–1.26). Additionally, those in the highest PM2.5 exposure quartile (Q4) had significantly higher odds of PTB (OR = 1.46, 95% CI: 1.11–1.93) than those in the lowest quartile (Q1) during the complete pregnancy period. PM2.5 exposure during the preconception, first-, second-, and third-trimester periods was not significantly associated with PTB. Place of residence and distance to healthcare were significant effect modifiers of the association between complete-pregnancy PM2.5 exposure and PTB. The exposure-response analysis indicated a nonlinear association, with a steeper increase in the predicted probability of PTB at higher PM2.5 concentrations. Our study revealed a significant association between PM2.5 exposure during pregnancy and increased odds of PTB. These findings highlight the need for targeted specific interventions to reduce air pollution exposure and protect vulnerable populations.