Preterm premature rupture of membranes (PROM) is the leading identifiable predisposing factor for preterm birth. Although maternal exposure to air pollution can potentially have an impact on preterm PROM, there is no available evidence on such an impact. In this study, based on 5,555 singleton births occurring in Barcelona, Spain (2002 -2005 , we investigated the associations of maternal exposure to nitrogen dioxide, nitrogen oxides, and particulate matter with aerodynamic diameters of ≤2.5 µm

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... PM 2.5 ), 2.5 µm-10 µm, and ≤10 µm and PM 2.5 light absorption with preterm PROM and gestational age at the rupture of membranes (ROM). We utilized temporally adjusted land-use regression models to predict pollutant levels at each subject's home address during each week of her pregnancy. We conducted matched (according to the length of exposure) case-control analyses to estimate the preterm PROM risk associated with 1 interquartile-range increase in exposure levels during the entire pregnancy and during the last 3 months prior to ROM. We found an increase in preterm PROM risk of up to 50% (95% confidence interval: 4, 116) and a 1.3-day (95% confidence interval: −1.9, −0.6) reduction in gestational age at ROM associated with PM 2.5 absorbance, nitrogen dioxide exposure, and nitrogen oxide exposure during the entire pregnancy and the last 3 months prior to ROM. air pollution; land-use regression; maternal exposure; nitrogen oxides; particulate matter; pregnancy; premature rupture of membranes; preterm birth Abbreviations: CI, confidence interval; IQR, interquartile range; LUR, land-use regression; MEDEA, Mortalidad en áreas pequeñas Españolas y Desigualdades Socioeconómicas y Ambientales; PM 2.5 , particulate matter with an aerodynamic diameter less than or equal to 2.5 µm; PM 2.5-10 , particulate matter with aerodynamic diameters between 2.5 µm and 10 µm; PM 10 , particulate matter with an aerodynamic diameter less than or equal to 10 µm; PROM, premature rupture of membranes; ROM, rupture of membranes. a Numbers in parentheses, interquartile range. b Maternal body mass index at booking time, calculated as weight (kg)/height (m) 2 . c Including vaginal bleeding during pregnancy, congenital uterine malformations, and/or uterine myoma. Air Pollution and Preterm PROM 203