The acute effect and lag effect analysis between exposures to ambient air pollutants and spontaneous abortion: a case-crossover study in China, 2017–2019

INTRODUCTION: Recent studies demonstrated that living in areas with high ambient air pollution may have adverse effects on pregnancy outcomes, but few studies have investigated its association with spontaneous abortion. Further investigation is needed to explore the acute effect and lag effect of air pollutants exposure on spontaneous abortion. OBJECTIVE: To investigate the acute effect and lag effect between exposure to ambient air pollutants and spontaneous abortion. METHODS: Research data of spontaneous abortion were collected from the Chongqing Health Center for Women and Children (CQHCWC) in China. The daily ambient air pollution exposure measurements were estimated for each woman using inverse distance weighting from monitoring stations. A time-stratified, case-crossover design combined with distributed lag linear models was applied to assess the associations between spontaneous pregnancy loss and exposure to each of the air pollutants over lags 0–7 days, adjusted for temperature and relative humidity. RESULTS: A total of 1399 women who experienced spontaneous pregnancy loss events from November 1, 2016, to September 30, 2019, were selected for this study. Maternal exposure to particulate matter 2.5 (PM(2.5)), particle matter 10 (PM(10)) nitrogen dioxide (NO(2)), and sulfur dioxide (SO(2)) exhibited a significant association with spontaneous abortion. For every 20 μg/m(3) increase in PM(2.5), PM(10), NO(2), and SO(2), the RRs were 1.18 (95% CI: 1.06, 1.34), 1.12 (95% CI, 1.04–1.20), 1.15 (95% CI: 1.02, 1.30), and 1.92 (95% CI: 1.18, 3.11) on lag day 3, lag day 3, lag day 0, and lag day 3, respectively. In two-pollutant model combined with PM(2.5) and PM(10), a statistically significant increase in spontaneous abortion incidence of 18.0% (RR = 1.18, 95% CI: 1.06, 1.32) was found for a 20 μg/m(3) increase in PM(2.5) exposure, and 11.2% (RR = 1.11, 95% CI: 1.03, 1.20) for a 20 μg/m(3) increase in PM(10) exposure on lag day 3, similar to single-pollutant model analysis. CONCLUSION: Maternal exposure to high levels of PM(2.5), PM(10), NO(2), and SO(2) during pregnancy may increase the risk of spontaneous abortion for acute effects and lag effects. Further research to explore sensitive exposure time windows is needed.