The Association between Preterm Birth and Ambient Air Pollution Exposure in Shiyan, China, 2015-2017.

Qihao Chen,Jingling Liao,Yuren Zhou,Kuizhuang Jiao,Haomin Yang,Xiaodie Wang,Zhan Ren,Yunfei Qiu,Yujie Liu,Lu Ma

doi:10.3390/ijerph18084326

Abstract

Shortening of the gestational duration has been found associated with ambient air pollution exposure. However, the critical exposure windows of ambient air pollution for gestational duration remain inconsistent, and the association between ambient air pollution and early term births (ETB, 37 to 38 weeks) has rarely been studied relative to preterm births (PTB, 28–37 weeks). A time-series study was conducted in Shiyan, a medium-sized city in China. Birth information was collected from the Shiyan Maternity and Child Health Hospital, and 13,111 pregnant women who gave birth between 2015 and 2017 were included. Data of the concentrations of air pollutants, including PM10, PM2.5, NO2, and SO2 and meteorological data, were collected in the corresponding gestational period. The Cox regression analysis was performed to estimate the relationship between ambient air pollution exposure and the risk of preterm birth after controlling the confounders, including maternal age, education, Gravidity, parity, fetal gender, and delivery mode. Very preterm birth (VPTB, 28–32 weeks) as a subtype of PTB was also incorporated in this study. The risk of VPTB and ETB was positively associated with maternal ambient air pollution exposure, and the correlation of gaseous pollutants was stronger than particulate matter. With respect to exposure windows, the critical trimester of air pollutants for different adverse pregnancy outcomes was different. The exposure windows of PM10, PM2.5, and SO2 for ETB were found in the third trimester, with HRs (hazard ratios) of 1.06 (95%CI: 1.04, 1.09), 1.07 (95%CI: 1.04, 1.11), and 1.28 (95%CI: 1.20, 1.35), respectively. However, for NO2, the second and third trimesters exhibited similar results, the HRs reaching 1.10 (95%CI: 1.03, 6.17) and 1.09 (95%CI: 1.03,1.15), respectively. This study extends and strengthen the evidence for a significant correlation between the ambient air pollution exposure during pregnancy and the risk of not only PTB but, also, ETB. Moreover, our findings suggest that the exposure windows during pregnancy vary with different air pollutants and pregnancy outcomes.

Highlights

After controlling the confounders, which included maternal age, education level, fetal gender, gravidity, and parity, we found that the ambient air pollution exposure was significantly associated with ETB and VPTB in the whole pregnancy (Table 2)
The exposure to air pollution during the first trimester was more significantly associated with VPTB, while the exposure window of ETB was observed in the second half of pregnancy, especially in the third trimester
Previous studies have not reached a consensus about the key window period of ambient air pollution exposure for shortened gestation [14], there has been numerous emerging evidence suggesting that the ambient air pollution exposure in the second half of pregnancy exhibits a stronger connection with an increasing risk of adverse pregnancy outcomes