Ambient Air Pollution Exposure around Conception Increased the Risk of Miscarriage

Abstract

Introduction: The impact of ambient air pollution (AAP) exposure on miscarriage is unclear. This study aims to examine AAP exposure on the risk of miscarriage and to investigate the critical window of exposure.Methods: A total of 201 women in early pregnancy (4-6 weeks) were recruited in this prospective cohort from Beijing during May 2016 to May 2017, and 178 were followed during the second and the third trimesters, and at delivery. The participants provided residential and demographic information, disease history, health habits, and occupational exposures in the baseline survey. Events of miscarriage including spontaneous abortion and embryonic loss were self-reported during the follow-up periods. AAP including particulate matter 2.5 (PM2.5), nitrogen dioxide (NO2), and ozone (O3) from the 35 monitoring stations in Beijing were collected. Land Use Regression model estimated the participants’ biweekly spatial AAP exposure from 8 weeks before conception till 20 weeks after. Log-binomial regression was used to assess the association of AAP exposure with the risk of miscarriage adjusted for parental age, maternal body mass index at baseline, and history of miscarriage or abortion.Results: A total of 22 (12.4%) participants reported miscarriage during 6-20 weeks of their pregnancy. APP exposure varied across the time period with ranges of 20.9 – 207.6 ug/m3 for PM2.5, 10.7 - 109.0 ug/m3 for NO2, and 11.8 - 165.7 ug/m3 for O3. The risk of miscarriage was about 4 times higher (risk ratio = 3.85, 95% confidence interval: 1.13 - 13.25) in women exposed to the highest tertile of PM2.5 (Median: 74.2, Interquartile range[IQR]: 35.81) compared to women exposed to the lowest tertile of PM2.5 (Median:55.87, IQR: 4.69) during the first two weeks of pregnancy. Risk of miscarriage was not significantly associated with AAP exposures during other periods.Conclusion: Exposure to high level of PM2.5 during the first two weeks of pregnancy may increase the risk of miscarriage.