Nitrogen dioxide exposure during pregnancy and risk of spontaneous abortion: a case-control study in China

Abstract

Background Evidence on the relationship between prenatal exposure to NO 2 and CO and spontaneous abortion (SAB) is insu cient. We investigated whether there is an association between maternal exposure to nitrogen dioxide (NO 2) and carbon monoxide (CO) before and during pregnancy and SAB. Methods We conducted a case-control study using medical records of 2445 pregnant women who admitted for abortion prior to 20 weeks of gestational age from January 2014 to December 2019 at a tertiary-care hospital in Shanghai, China. Of the 2445 participants, 1075 were SAB cases and 1370 were healthy controls (underwent elective abortions). Maternal exposure to NO 2 and CO before and during pregnancy was estimated using daily air pollution concentration data. Multivariable logistic regression models were constructed to quantify the relationships between maternal exposure to NO 2 or CO and the risk of SAB while controlling for potential confounders. Results NO 2 exposure levels during pregnancy were signi cantly higher in SAB cases than in healthy controls (42.26 vs 40.67, P < 0.01). NO 2 exposure during pregnancy was positively associated with the risk of SAB. An interquartile range (16 µg/m 3) increase in NO 2 exposure was associated with 67% increase in the odds of SAB (OR = 1.67, 95% CI, 1.28, 2.18). Analyses of associations by quartile of NO 2 exposure showed that elevated NO 2 exposure during pregnancy was associated with increased odds of SAB in linear doseresponse manners. Compared with the lowest quartile of NO 2 exposure, the odds of SAB in the fourth quartile of NO 2 exposure increased 60% (OR = 1.60, 95% CI, 1.03-2.49). No associations of CO exposure with SAB risk were observed. Conclusion Our study suggested that exposure to NO 2 during early pregnancy was associated with increased risk of SAB. Further studies are need to con rm our results and explore the potential biological mechanism underlying these associations.