ASSOCIATIONS OF GESTATIONAL EXPOSURE TO TOXIC METALS AND ALLERGIC OUTCOMES IN CHILDREN: A META-ANALYSIS



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Abstract

Objective: Because of their immunotoxic qualities and capacity to cross the placental barrier, exposure to toxic metals during pregnancy may have an impact on the development of allergy disorders in offspring. However, results from different research continue to be conflicting. The purpose of this meta-analysis was to determine the associations between gestational exposure to certain heavy metals and the risk of allergic outcomes to the child.

Methods: This systematic literature review was run through six databases, that is, Embase, PubMed, Scopus, Web of Science, Cochrane Library, and Google Scholar, up to February 2025. Included were observational studies on prenatal exposures to heavy metals and allergic conditions later in life. The pooled odds, risk, and hazard ratios, as well as standardized mean differences in body weight, were computed using the random-effects model. Systematic assessment was performed on heterogeneity, publication bias, and study quality.

Results: The meta-analysis that embodied 14 cohort studies with a composite sample of 292,057 participants from Korea, Taiwan, Japan, China, Mexico, France, Spain, and Sweden looked at the relationship between the prenatal exposure of distinct heavy metals most associated with lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), and nickel (Ni), and allergic conditions during early childhood, such as asthma, atopic dermatitis, rhinitis, wheezing and food allergy. Across the metals investigated, none presented statistically significant evidence of relationship with any allergic outcome. The pooled odds ratio (ORs) for prenatal lead exposure and asthma, OR were 1.05 (95% CI: 0.85-1.24); for mercury exposure and atopic dermatitis, the OR of 1.00 (95% CI: 0.97-1.04); while for cadmium exposure and atopic dermatitis, it was 1.06 (95%CI: 0.87-1.25), respectively. Heterogeneity in studies was low to moderate, while funnel plot analyses did not reveal significant evidence for publication bias.

Conclusion: This meta-analysis found no definitive evidence for an association between prenatal exposure to selected toxic metals and allergic diseases in children. While biologically plausible mechanisms exist, current observational data do not substantiate a clear link. Future studies need to resolve these methodological limitations and investigate interactions between metals, timing of exposure, and genetic susceptibility.

About the authors

Neda Fakhr Ghasemi

Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran

Email: FakhrghasemiN4021@mums.ac.ir

Researcher, Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran;

Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran;

Iran, Islamic Republic of

Narges Tayari

University of Medical Sciences, Bandar Abbas, Iran

Email: Narges.tayari@yahoo.com

Student research committee, Mother and Child Welfare Research Center, Hormozgan University of Medical Sciences, Bandar Abbas, Iran;

Mother and Child Welfare Research Center, Hormozgan University of Medical Sciences, Bandar Abbas, Iran;

Iran, Islamic Republic of

Sourena Mohammad Hashem

University of Medical Science, Qazvin, Iran

Email: sourena8181@gmail.com

Student Research Committee, Faculty of Medicine, Qazvin University of Medical Science, Qazvin, Iran;

Iran, Islamic Republic of

Elham Yadegarifard

University of Medical Sciences, Bandar Abbas, Iran

Email: Iranemydf99@gmail.com

Student Research Committee, Faculty of Medicine;

Hormozgan University of Medical Sciences, Bandar Abbas, Iran;

Iran, Islamic Republic of

Ali Molavi

Ilam University of Medical Science, Ilam, Iran

Email: ali.re.mo.1382@gmail.com

Medical Student;

Ilam University of Medical Science, Ilam, Iran;

Iran, Islamic Republic of

Akram Ansari

Shantou Univercity MedicL College, Shantou, Guangdong

Email: China22Akramansari@stu.edu.cn

Student Research Committee, Shantou Univercity MedicL College, Shantou, Guangdong China;

Shantou Univercity MedicL College, Shantou, Guangdong;

China

Mojan Ayati

University of Szeged, Szeged, Hungary

Email: mojn.ayati@gmail.com

Student Research Committee, School of Medicine, University of Szeged, Szeged, Hungary;

School of Medicine, University of Szeged, Szeged, Hungary;

Hungary

Niloofar Deravi

Shahid Beheshti University of Medical Sciences, Tehran, Iran

Email: niloofar.deravi@gmail.com

Researcher, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran;

Student Research Committee, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran;

Iran, Islamic Republic of

Elham Keikha

Shahid Beheshti University of Medical Sciences, Tehran, Iran

Author for correspondence.
Email: Keykha6454@yahoo.com

Student Research Committee, Department of Internal Medicine Shahid Labbafinezhad Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran;

Department of Internal Medicine Shahid Labbafinezhad Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran;

Iran, Islamic Republic of

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