Analysis of short-term and sub-chronic effects of ambient air pollution on preterm birth in central China

Recently, an increasing number of studies have reported the possible linkage between maternal exposure to ambient air pollution and adverse birth outcomes. This retrospective cohort study aimed to evaluate the effect of short-term and sub-chronic exposure to air pollutants on preterm birth occurred in Shiyan and Jingzhou, Hubei province, China from 2014 to 2016. General additive models (GAM) were performed to examine the impact of the daily and cumulative weekly air pollutants exposure. The non-linear patterns between adverse birth outcomes and weather condition were assessed by including penalized smoothing splines in the model. The demographic characteristics of pregnant women were also included in the model as covariates. A total of 16,035 cases were analyzed. Significant short-term effects of air pollution exposure at lag 1 day on preterm birth were observed. In adjusted single-pollutant city-specific model, the association between acute air pollutant exposure and preterm birth was significant in Shiyan (PM_2.5: OR = 1.066, 95% CI 1.027, 1.106; PM₁₀: OR = 1.048, 95% CI 1.022, 1.076; O₃: OR = 1.029, 95% CI 1.004, 1.056) and Jingzhou (PM_2.5: OR = 1.037, 95% CI 1.008, 1.068; PM₁₀: OR = 1.025, 95% CI 1.007, 1.043; SO₂: OR = 1.082, 95% CI 1.023, 1.144; NO₂: OR = 1.211, 95% CI 1.098, 1.335) per 10 μg/m³ increment. Also, weekly average cumulative air pollution exposure was significantly associated with preterm birth in both areas.