Prenatal air pollution exposure and adverse birth outcomes: windows of susceptibility and socio-economic inequalities

BACKGROUND AND AIM: Air pollution exposure has been associated with adverse birth outcomes. However, few studies have investigated potential gestational windows of susceptibility. Further, the extent to which this association differs across socioeconomic status (SES) is underexplored. Therefore, the aim of this study is to investigate windows of susceptibility and explore potential social inequalities in the association between prenatal air pollution exposure and adverse birth outcomes. METHODS: We used a Spanish national-wide birth registry study which includes all newborns born between 2009 and 2010 (n=353,750) and whose mothers resided in the peninsula or the Balearic Islands. Maternal exposures to particulate matter with an aerodynamic diameter of 10 µm (PM10), 2.5 µm (PM2.5), and 2.5-10µm (PMcoarse) were estimated at the residential address throughout pregnancy on a daily basis using spatiotemporal land use machine-learning models. Birth outcomes (i.e., birth weight, gestational age, prematurity, and small or large for gestational age) and SES characteristics of the parents (i.e., education, occupation, ethnicity, area-level deprivation index) were obtained from the registry. Confounder adjusted associations between pollutant concentrations and birth outcomes, windows of susceptibility, and SES disparities were examined using regression models. RESULTS:Higher air pollution concentrations were associated with lower birth weight and increased prematurity [e.g., 20 gram decrease in birth weight (95%CI -25.3, -15.2) per each 10μg/m3 increase in PM10]. Results revealed that exposure during the third trimester were driving these associations and that effect on birth weight and prematurity was greater in magnitude for children from low SES families. Air pollution exposure was not associated with being small or large for gestational age. CONCLUSIONS:Exposure to air pollution during pregnancy was associated with adverse birth outcomes, with the third trimester of pregnancy being the most susceptible window. A pattern of social inequality was observed in this association, with a greater impact on newborns from families with fewer resources. KEYWORDS: Air pollution, birth outcomes, socio-economic inequalities, windows of susceptibility, pregnancy