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Abstract Background Nitrogen dioxide (NO 2) is a typical indicator of traffic-related air pollution, and few studies with exposure assessment of high resolution have been conducted to explore its association with preterm birth in China. Objectives To investigate the association between NO 2 exposure based on a land use regression (LUR) model and preterm birth in Shanghai, China. Methods A retrospective cohort study was performed among 25,493 singleton pregnancies in a major maternity hospital in Shanghai, China, from 2014 to 2015. A temporally adjusted LUR model was used to predict the prenatal exposure to NO 2 based on residence address of each gravida. Logistic regression was performed to evaluate the associations of ambient NO 2 exposure with preterm birth during six exposure periods, including the entire pregnancy, the first trimester, the second trimester, the third trimester, the last month, and the last week before delivery. Sensitivity analysis with a matched case-control design was conducted to test the robustness of the association between NO 2 exposure and preterm birth. Results The average NO 2 concentrations during the entire pregnancy was 48.23 µg/m3 among all participants. A 10 µg/m3 increase in NO 2 concentrations was associated with preterm birth, with an adjusted odds ratio of 1.03 (95% confidence interval [CI]: 0.96,1.10) for exposures during the entire pregnancy, 1.00 (95%CI: 0.95,1.06) in the first trimester, 1.01 (95%CI: 0.96,1.07) in the second trimester, 1.07 (95%CI: 1.02,1.13) in the third trimester, 1.10 (95%CI: 1.04,1.15) and 1.05 (95%CI: 1.00,1.09) in the month and week before delivery, respectively. The results of the matched case–control analysis were generally consistent with those of main analyses. Conclusion NO 2 may increase the risk of preterm birth, especially for exposures during the third trimester, the month and the week before delivery in Shanghai, China. Graphical abstract fx1 Highlights • The first study evaluating the impacts of LUR-derived NO 2 on preterm birth in China. • The LUR model of NO 2 has a high spatial resolution and predictive ability. • The impacts of NO 2 exposure on preterm birth varied by different trimesters. • NO 2 exposure during the third trimester may increase the risk of preterm birth. [ABSTRACT FROM AUTHOR]

Findings for impacts of outdoor air pollutants on birth outcomes were controversial. We performed a retrospective observational study in 2527 preschoolers of Shanghai, China and investigated associations of duration-averaged concentrations of outdoor sulphur dioxide (SO 2), nitrogen dioxide (NO 2), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM 10) in different months and trimesters of gestation, with preterm birth (PB), low birth weight (LBW), term low birth weight (T-LBW), and small for gestational age (SGA). Daily concentrations of outdoor air pollutants were collected in each residence-located district. Parents reported health information. In the multivariate logistic regression analyses, exposures to outdoor NO 2 were consistently associated with the higher odds of LBW and T-LBW. These associations were generally stronger for early months than for later months of the gestation. Adjusted odds ratios generally were larger in multi-pollutant model than in single-pollutant model. Exposure to NO 2 in the first month of the gestation was significantly associated with T-LBW (adjusted OR, 95%CI: 1.91, 1.02–3.58 for increment of interquartile range (18.5 μg/m3); p -value = 0.044) in multi-pollutant model. This association was stronger in girls, renters, and children whose mothers ≥30 years-old, with household dampness-related exposures, and with parental smoking during pregnancy. Our results indicate that exposure to NO 2 during gestation perhaps is a risk factor for LBW and T-LBW, and effects of NO 2 exposures could be greater during early periods than during later periods of gestation. • A retrospective observational study in 2527 preschoolers was conducted. • Exposures to outdoor NO 2 consistently associated with LBW and T-LBW. • These associations were stronger for early months than for later months. • Adjusted ORs were larger in multi-pollutant than single-pollutant model. • No significant associations were found of SO 2 and PM 10 with all outcomes. [ABSTRACT FROM AUTHOR]