Impact of climate change on spontaneous abortion: a systematic review and meta-analysis.

PURPOSE: This systematic review and meta-analysis was conducted to synthesize the existing evidence on the association between climate change-related factors and spontaneous abortion.

PATIENTS AND METHOD: We conducted a systematic literature search across PubMed, Embase, MEDLINE, Web of Science, PsycINFO, and Google Scholar for studies published in English. Eligible studies included all observational study designs that assessed the relationship between climate-related exposures and spontaneous abortion. Quality assessment was performed using the Newcastle-Ottawa Scale. Random-effects models were applied to pool effect estimates, expressed as odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup and sensitivity analyses were conducted to explore heterogeneity.

RESULTS

Of the 19,167 records, 37 studies met the eligibility criteria. Pooled estimates demonstrated significant positive associations between maternal exposure to climate-related factors, including air pollution, high ambient temperature, floods, and wildfire smoke, and spontaneous abortion: increased risks were observed with exposure to sulfur dioxide (OR = 1.60, 95% CI: 1.20-2.13), ozone (OR = 1.27, 95% CI: 1.01-1.60), carbon monoxide (OR = 1.48, 95% CI: 1.06-2.06), nitrogen dioxide (OR = 1.17 95% CI: 1.00-1.38), particulate matter (OR = 1.15, 95% CI: 1.06-1.24), and high ambient temperature/heat exposure (OR = 1.39, 95% CI: 1.07-1.79). Subgroup analyses showed that exposure to high temperature was associated with an elevated risk of spontaneous abortion among women living in lower-middle-income countries and abortions before 20 weeks of gestation. Evidence on floods and wildfire smoke exposure also suggested an increased risk of spontaneous abortion.

CONCLUSION

Climate change-related exposures are significantly associated with an increased risk of abortion, particularly spontaneous abortion. These findings underscore the urgent need to integrate reproductive health into climate adaptation strategies, strengthen surveillance systems, and develop climate-resilient health infrastructures to protect vulnerable populations.

SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251120772, PROSPERO CRD420251120772.