The correlation between chronic exposure to particulate matter and spontaneous abortion: A meta-analysis

Background: Spontaneous abortion (SAB) brings serious physical and psychological sequelae to women and their families. Though a growing body of individual studies have suggested the possible linkage between chronic particulate matter (PM) exposure and risks of SAB, the provided results were rather contradictory. We therefore performed an evidence-based meta-analysis.

Methods: We systematically searched the PubMed, EMBASE and Web of Science databases for available studies published before February 1, 2021 which reported associations between PM exposure and SAB. Corresponding models were applied to combine relative risks (RRs) and their confidence intervals (CIs) from eligible studies according to heterogeneity test. The GRADEpro app was used to evaluate the certainty of evidence. Sensitivity analyses and a publication bias assessment were also utilized to determine the stability of results.

Results: Of the initial 2358 citations, 6 papers examining the chronic effects of PM exposure were deemed eligible and a total population of approximately 723,000 was observed. Pooled RR for SAB risks associated with a 10 μg/m³ increase in fine particulate matter (PM_2.5) and particulate matter ≤ 10 μm in aerodynamic diameter (PM₁₀) were 1.20 (95%CI: 1.01-1.40) and 1.09 (95%CI: 1.02-1.15), respectively. The GRADE results of PM_2.5 and PM₁₀ were both categorized as "moderate" certainty evidence.

Conclusion: Our findings revealed a significant increase of SAB hazards related with maternal PM exposure, and this study may therefore provide new evidence for personal protection to improve reproductive health.