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. 2016 Feb 5;124(8):1283–1290. doi: 10.1289/ehp.1510266

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Odds ratios and 95% confidence intervals of spontaneous-only and combined spontaneous and medically indicated early preterm births (< 32 weeks) per 10 μg/m³ of overall first- and second-trimester exposure to PM_2.5 (A) and 20 ppb of NO₂ (B). The adjusted model included individual demographics (mother’s ethnicity/birthplace, age, education, parity, Medicaid status, prepregnancy BMI, sex of infant, conception year), SDI, hospital rates of medically indicated births and random intercept by hospital ID.