The association between maternal exposure to ambient particulate matter of 2.5 μm or less during pregnancy and fetal congenital anomalies in Yinchuan, China: A population-based cohort study

Abstract Background Few studies from western countries have linked prenatal exposure to ambient particulate matter 2.5 ) with increased risk of congenital anomalies. However, the results are mixed. Particularly, evidence is limited for Chinese pregnant women. Methods In this retrospective cohort study, we matched the data of all pregnant women laboured in public hospitals during 2015–2016 in Yinchuan, a capital city of northwest China and the data of daily average PM 2.5 , nitrogen dioxide (NO 2 ), sulphur dioxide (SO 2 ) and ozone (O 3 ) concentrations of the nearest monitor station. We calculated a time-dependent exposure over the entire pregnancy for each woman. We used a time varying Cox proportional hazards model to explore the association between PM 2.5 exposure and the risk of congenital anomalies, after adjusting for individual confounders and other pollutants. Results A total of 39,386 singleton live births were included in the study, and 530 (1.35%) were with congenital anomalies. An increase of 10 μg/m 3 in PM 2.5 exposure over the entire pregnancy was significantly associated with increased risk of congenital anomalies, with hazard ratio (HR) of 1.35 [95% confidence interval (95%CI): 1.16, 1.58]. For subtype analyses, PM 2.5 exposure exhibited a significant association with cardiac anomalies and other unclassifiable anomalies, with HRs of 1.60 (95%CI: 1.24, 2.08) and 1.42 (95%CI: 1.07, 1.89), respectively. The impacts of PM 2.5 exposure on orofacial anomalies and musculoskeletal anomalies were not significant. Conclusion Our results indicate high concentration of PM 2.5 could increase the risk of congenital anomalies among Chinese, especially for cardiac anomalies. Self-protective measures involving reducing PM 2.5 pollution exposure during pregnancy as well as environmental policies aiming to restrict PM 2.5 emission could be helpful to reduce the burden of cognitional anomalies.