Air Pollution and Risk of Placental Abruption: A Study of Births in New York City, 2008-2014.

We evaluated the associations amongst fine particulate matter (PM2.5 <12, 12-14, and ≥15 μg/m3) and nitrogen dioxide (NO2 <26, 26-29, and ≥30 ppb) and abruption in prospective cohort of 685,908 pregnancies in New York City (2008-2014). In co-pollutant analyses these associations were examined using distributed lag non-linear models based on Cox models. The prevalence of abruption was 0.9% (n=6025). Compared to PM2.5 <12 μg/m3, women exposed to PM2.5 ≥15 μg/m3 in the third trimester experienced higher abruption rate (hazard ratio [HR] 1.68, 95% confidence interval [CI]: 1.41, 2.00). Compared to NO2 <26 ppb, women exposed to 26-29 ppb (HR 1.11, 95% CI: 1.02, 1.20) and ≥30 ppb (HR 1.06, 95% CI: 0.91, 1.24) in the first trimester were associated with higher abruption rate. Compared to both PM2.5 and NO2 <95th percentile in the third trimester, rates of abruption were increased with both PM2.5 and NO2 ≥95th percentile (HR 1.44, 95% CI: 1.15, 1.80) and PM2.5 ≥95th percentile and NO2 <95th percentile (HR 1.43 95% CI: 1.23, 1.66). Increased PM2.5 levels in the third trimester and NO2 in the first trimester are associated with elevated abruption rates, suggesting that these exposures may be important triggers of premature placental separation through different pathways.