Association between Maternal Short-Term Exposure to Ambient Air Pollution and the Risk of Fetal Distress: A Matched Case-Control Study

BACKGROUND:Ambient air pollution has been linked to gestational complications. However, the evidence on the relationship between air pollution and fetal distress is limited. OBJECTIVES:To investigate the relationship between maternal short-term air pollution exposure and fetal distress, and to identify a potential susceptible population. METHODS:This matched case-control study, involving 313 pregnancy women with fetal distress was conducted in Xi'an, the largest city in Northwest China from 2013 to 2016. Each woman with fetal distress was randomly matched with four women without fetal distress of the same age, same gestational week, and registration in the same period (n = 1252). Inverse distance-weighted (IDW) interpolation was applied to estimate maternal air pollution exposure based on the residential addresses. We employed conditional logistic regression model to evaluate the relationship between air pollutants and fetal distress. Distributed lag nonlinear model (DLNM) was performed to examine the exposure-response relationship between air pollutants and fetal distress. RESULTS:Maternal short-term exposure to PM10, PM2.5-10 (PMc), SO2, NO2, and CO was associated with increased risk of fetal distress. Each 10 μg/m3 increment in PM10, PMc, SO2 at lag 014, and NO2 at lag 010, the odds ratio (ORs) of fetal distress were 1.027 (95 % confidence interval (CI): 1.004, 1.050), 1.058 (95 % CI: 1.014, 1.105), 1.140 (95 % CI: 1.029, 1.264), and 1.158 (95 % CI: 1.046, 1.283), respectively. Similarly, with a 0.1 mg/m3 increment in CO at lag 014, the OR of fetal distress was 1.029 (95 % CI: 1.002, 1.058). Stratified analyses showed that the estimate associations of PM10, PM2.5 and CO appeared to be stronger, although not statistically significantly, among women with gestational complications. CONCLUSION:Maternal short-term exposure to ambient air pollution may increase the risk of fetal distress. Understanding the detrimental role of air pollution in fetal distress can help us better develop preventative methods in reducing its' impact on maternal and fetal health.