Air Pollution and Stillbirth Risk: Exposure to Airborne Particulate Matter during Pregnancy Is Associated with Fetal Death

OBJECTIVE: To test the hypothesis that exposure to fine particulate air pollution (PM(2.5)) is associated with stillbirth. STUDY DESIGN: Geo-spatial population-based cohort study using Ohio birth records (2006-2010) and local measures of PM(2.5), recorded by the EPA (2005-2010) via 57 monitoring stations across Ohio. Geographic coordinates of the mother’s residence for each birth were linked to the nearest PM(2.5) monitoring station and monthly exposure averages calculated. The association between stillbirth and increased PM(2.5) levels was estimated, with adjustment for maternal age, race, education level, quantity of prenatal care, smoking, and season of conception. RESULTS: There were 349,188 live births and 1,848 stillbirths of non-anomalous singletons (20-42 weeks) with residence ≤10 km of a monitor station in Ohio during the study period. The mean PM(2.5) level in Ohio was 13.3 μg/m(3) [±1.8 SD, IQR(Q1: 12.1, Q3: 14.4, IQR: 2.3)], higher than the current EPA standard of 12 μg/m(3). High average PM(2.5) exposure through pregnancy was not associated with a significant increase in stillbirth risk, (adj)OR 1.21(95% CI 0.96,1.53), nor was it increased with high exposure in the 1(st) or 2(nd) trimester. However, exposure to high levels of PM(2.5) in the third trimester of pregnancy was associated with 42% increased stillbirth risk, (adj)OR 1.42(1.06,1.91). CONCLUSIONS: Exposure to high levels of fine particulate air pollution in the third trimester of pregnancy is associated with increased stillbirth risk. Although the risk increase associated with high PM(2.5) levels is modest, the potential impact on overall stillbirth rates could be robust as all pregnant women are potentially at risk.