Abstract
BACKGROUND AND AIM: There is minimal evidence of relationships between maternal air pollution exposure and spontaneous premature rupture of membranes (SPROM), a critical obstetrical problem that can significantly increase maternal and fetal mortality and morbidity. No prior study has explored the PROM risk related to specific components of particulate matter with aerodynamic diameters of ≤ 2.5 µm (PM₂.₅). We examined associations between maternal exposure to nitrogen dioxide (NO₂), ozone (O₃), PM₂.₅, PM10, and PM₂.₅ constituents and SPROM. METHOD: A large retrospective cohort study was conducted and included 427,870 singleton live births from Kaiser Permanente Southern California during 2008-2018. Monthly averages of NO₂, O₃ (8-h daily maximum), PM₂.₅, and PM10 were measured using empirical Bayesian kriging based on measurements from monitoring stations. Data on PM₂.₅ sulfate, nitrate, ammonium, organic matter, and black carbon were obtained from a fine-resolution model. A discrete time approach with pooled logistic regressions was used to estimate associations throughout the pregnancy and based on trimesters and gestational months. The quantile-based g-computation models were fitted to examine the effects of 1) the air pollution mixture of four pollutants of interest and 2) the mixture of PM₂.₅ components. RESULTS: There were 37,857 SPROM cases (8.8%) in our study population. We observed relationships between maternal exposure to all four pollutants and SPROM. PM₂.₅ sulfate, nitrate, ammonium, and organic matter were associated with higher SPROM risks in the single-pollutant model. Mixture analyses demonstrated that the overall effects of the air pollution mixture and PM₂.₅ mixture in this study were mainly driven by O₃ and PM₂.₅ nitrate, respectively. Underweight mothers had a significantly higher risk of SPROM associated with NO₂. CONCLUSIONS: Our findings add to the literature on associations between air pollution exposure and SPROM. This is the first study reporting the impact of PM₂.₅ constituents on SPROM.