Association between female circulating heavy metal concentration and abortion: a systematic review and meta-analysis

OBJECTIVE: This study aimed to evaluate the association between blood heavy metal (zinc (Zn), copper (Cu), lead (Pb), and cadmium (Cd)) concentrations and spontaneous abortion (SA) and recurrent pregnancy loss (RPL) and explore the possible endocrine dysfunction associated with it. METHODS: A literature search was performed in the PubMed, Embase, Cochrane Library, and Web of Science databases up to April 2023. The overall effects were expressed as the standard mean difference (SMD). Subgroup analysis was performed according to the type of abortion (SA or RPL). Stata 16.0 was utilized for data analysis. RESULTS: Based on the integrated findings, abortion women showed significantly lower Zn (SMD = −1.05, 95% CI: −1.74 to −0.36, p = 0.003) and Cu concentrations (SMD = −1.42, 95% CI: −1.97 to −0.87, p <0.001) and higher Pb (SMD = 1.47, 95% CI: 0.89–2.05, p <0.001) and Cd concentrations (SMD = 1.15, 95% CI: 0.45–1.85, p = 0.001) than normal pregnant women. Subgroup analysis showed that Zn and Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with RPL, whereas Cu deficiency and Cd and Pb exposure were significantly (p <0.05) associated with SA. CONCLUSION: Zn and Cu deficiencies and Pb and Cd exposure were associated with abortion. Endocrine dysfunction, such as insulin resistance, vitamin D insufficiency, and abnormal thyroid and sex hormone concentrations, is thought to be involved in heavy metal-related abortion.