Traffic-Related Air Pollution and Pregnancy Loss

Abstract

Background. Traffic-related air pollution has been linked to multiple adverse pregnancy outcomes. However, few studies have examined pregnancy loss, targeting losses identified by hospital records, a large limitation as it does not capture events not reported to the medical system.Methods. We used a novel variation of the time-series design to determine the association, and identify the critical window of vulnerability, between week-to-week traffic-related air pollution and conceptions resulting in live births, using nitrogen dioxide (NO2) as a traffic emissions tracer. We used information from all live births recorded at Beth Israel Deaconess Medical Center (BIDMC) in Boston, MA (2000–2013) and all live births in Tel Aviv District, Israel (2010–2013). For exposure assessment, in Boston we used the average of 5 urban monitoring sites, while in Tel Aviv the district average of a spatio-temporal prediction model.Results: In Tel Aviv District, the strongest estimate was during the 16th gestational week; for every 10 ppb of NO2 we observed a decreased rate of live births (RR=0.82; 95%CI: 0.76–0.90), using live-birth identified conceptions to infer pregnancy losses. In Boston, the strongest estimate was during the 15th gestational week; we observed a RR = 0.87 (95%CI: 0.78–0.97), among women living within 60 km from BIDMC, and RR = 0.84 (95%CI: 0.74–0.96) in week 17 among those within 20 km from BIDMC.Conclusions: Using weekly conceptions ending in a live birth rather than identified pregnancy losses, we for the first time comprehensively considered the relationship between air pollution and all pregnancy loss throughout gestation. The observed results, with remarkable similarity in two independent locations, suggest that at levels of traffic pollution experienced in Boston and Israel, higher levels are associated with pregnancy loss with strongest estimates between the 10th–20th gestational weeks.