Effects of Radiofrequency Electromagnetic Field (RF-EMF) exposure on pregnancy and birth outcomes: A systematic review of experimental studies on non-human mammals

PAPER manual 2021 Systematic review Effect: mixed Evidence: Moderate

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Abstract

Abstract Background: The World Health Organization is coordinating an international project aimed at systematically reviewing the evidence regarding the association between radiofrequency electromagnetic field (RF-EMF) exposure and adverse health effects. Within the project, 6 topics have been prioritized by an expert group, which include reproductive health outcomes. Objectives: According to the protocol published in 2021, a systematic review and meta-analyses on the adverse effects of RF-EMF exposure during pregnancy in offspring of experimental animals were conducted. Methods: Three electronic databases (PubMed, Scopus and EMF Portal) were last searched on September 8 or 17, 2022. Based on predefined selection criteria, the obtained references were screened by two independent reviewers. Studies were included if they met the following criteria: 1) original, sham controlled experimental study on non-human mammals exposed in utero, published in peer-reviewed journals, 2) the experimental RF-EMF exposure was within the frequency range 100 kHz-300 GHz, 3) the effects of RF-EMF exposure on fecundity (litter size, embryonic/fetal losses), on the offspring health at birth (decrease of weight or length, congenital malformations, changes of sex ratio) or on delayed effects (neurocognitive alterations, female infertility or early-onset cancer) were studied. Study characteristics and outcome data were extracted by two reviewers. Risk of bias (RoB) was assessed using the Office of Health Assessment and Translation (OHAT) guidelines. Study results were pooled in a random effects meta-analysis comparing average exposure to no-exposure and in a dose-response meta-analysis using all exposure doses, after exclusion of studies that were rated at "high concern" for RoB. Subgroup analyses were conducted for species, Specific Absorption Rate (SAR) and temperature increase. The certainty of the evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Results: Eighty-eight papers could be included in this review. Effects on fecundity. The meta-analysis of studies on litter size, conducted at a whole-body average SAR of 4.92 W/kg, did not show an effect of RF-EMF exposure (MD 0.05; 95% CI -0.21 to 0.30). The meta-analysis of studies on resorbed and dead fetuses, conducted at a whole-body average SAR of 20.26 W/kg, showed a significant increase of the incidence in RF-EMF exposed animals (OR 1.84; 95% CI 1.27 to 2.66). The results were similar in the dose-response analysis. Effects on the offspring health at birth. The meta-analysis of studies on fetal weight, conducted at a whole-body average SAR of 9.83 W/kg, showed a small decrease in RF-EMF exposed animals (SMD 0.31; 95% CI 0.15 to 0.48). The meta-analysis of studies on fetal length, conducted at a whole-body average SAR of 4.55 W/kg, showed a moderate decrease in length at birth (SMD 0.45; 95% CI 0.07 to 0.83). The meta-analysis of studies on the percentage of fetuses with malformations, conducted at a whole-body average SAR of 6.75 W/kg, showed a moderate increase in RF-EMF exposed animals (SMD -0.45; 95% CI -0.68 to -0.23). The meta-analysis of studies on the incidence of litters with malformed fetuses, conducted at a whole-body average SAR of 16.63 W/kg, showed a statistically significant detrimental RF-EMF effect (OR 3.22; 95% CI 1.9 to 5.46). The results were similar in the dose-response analyses. Delayed effects on the offspring health. RF-EMF exposure was not associated with detrimental effects on brain weight (SMD 0.10; 95% CI -0.09 to 0.29) and on learning and memory functions (SMD -0.54; 95% CI -1.24 to 0.17). RF-EMF exposure was associated with a large detrimental effect on motor activity functions (SMD 0.79; 95% CI 0.21 to 1.38) and a moderate detrimental effect on motor and sensory functions (SMD -0.66; 95% CI -1.18 to -0.14). RF-EMF exposure was not associated with a decrease of the size of litters conceived by F2 female offspring (SMD 0.08; 95% CI -0.39 to 0.55). Notably, meta-analyses of neurobehavioural effects were based on few studies, which suffered of lack of independent replication deriving from only few laboratories. Discussion: There was high certainty in the evidence for a lack of association of RF-EMF exposure with litter size. We attributed a moderate certainty to the evidence of a small detrimental effect on fetal weight. We also attributed a moderate certainty to the evidence of a lack of delayed effects on the offspring brain weight. For most of the other endpoints assessed by the meta-analyses, detrimental RF-EMF effects were shown, however the evidence was attributed a low or very low certainty. The body of evidence had limitations that did not allow an assessment of whether RF-EMF may affect pregnancy outcomes at exposure levels below those eliciting a well-known adverse heating impact. In conclusion, in utero RF-EMF exposure does not have a detrimental effect on fecundi

AI evidence extraction

At a glance

Study type

Systematic review

Effect direction

mixed

Population

Non-human mammals (experimental animals) exposed in utero during pregnancy

Sample size

Exposure

Evidence strength

Moderate

Confidence: 86% · Peer-reviewed: yes

Main findings

Systematic review/meta-analyses of 88 sham-controlled experimental studies in non-human mammals exposed in utero (100 kHz–300 GHz) found no effect on litter size (MD 0.05; 95% CI -0.21 to 0.30; whole-body average SAR 4.92 W/kg). Increased resorbed/dead fetuses (OR 1.84; 95% CI 1.27 to 2.66; SAR 20.26 W/kg), decreased fetal weight (SMD 0.31; 95% CI 0.15 to 0.48; SAR 9.83 W/kg) and length (SMD 0.45; 95% CI 0.07 to 0.83; SAR 4.55 W/kg), and increased malformations (including OR 3.22; 95% CI 1.9 to 5.46 for litters with malformed fetuses; SAR 16.63 W/kg) were reported. Delayed effects showed no association for brain weight (SMD 0.10; 95% CI -0.09 to 0.29) and learning/memory (SMD -0.54; 95% CI -1.24 to 0.17), but detrimental associations for motor activity (SMD 0.79; 95% CI 0.21 to 1.38) and motor/sensory functions (SMD -0.66; 95% CI -1.18 to -0.14); neurobehavioral meta-analyses were based on few studies from few laboratories.

Outcomes measured

Fecundity (litter size)
Embryonic/fetal losses (resorbed and dead fetuses)
Fetal weight at birth
Fetal length at birth
Congenital malformations (percentage of fetuses with malformations; incidence of litters with malformed fetuses)
Offspring brain weight (delayed effect)
Learning and memory functions (delayed effect)
Motor activity functions (delayed effect)
Motor and sensory functions (delayed effect)
F2 female offspring fertility (litter size conceived by F2 female offspring)

Limitations

For most endpoints showing detrimental effects, certainty was rated low or very low.
Neurobehavioural meta-analyses were based on few studies with limited independent replication (few laboratories).
Limitations prevented assessment of effects at exposure levels below those eliciting a well-known adverse heating impact.
Some analyses excluded studies rated at 'high concern' for risk of bias (OHAT), potentially limiting available evidence.

Suggested hubs

who-icnirp (0.78)
Abstract describes a WHO-coordinated international project and systematic review protocol for RF-EMF health effects.

View raw extracted JSON

{
    "study_type": "systematic_review",
    "exposure": {
        "band": "RF",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Non-human mammals (experimental animals) exposed in utero during pregnancy",
    "sample_size": 88,
    "outcomes": [
        "Fecundity (litter size)",
        "Embryonic/fetal losses (resorbed and dead fetuses)",
        "Fetal weight at birth",
        "Fetal length at birth",
        "Congenital malformations (percentage of fetuses with malformations; incidence of litters with malformed fetuses)",
        "Offspring brain weight (delayed effect)",
        "Learning and memory functions (delayed effect)",
        "Motor activity functions (delayed effect)",
        "Motor and sensory functions (delayed effect)",
        "F2 female offspring fertility (litter size conceived by F2 female offspring)"
    ],
    "main_findings": "Systematic review/meta-analyses of 88 sham-controlled experimental studies in non-human mammals exposed in utero (100 kHz–300 GHz) found no effect on litter size (MD 0.05; 95% CI -0.21 to 0.30; whole-body average SAR 4.92 W/kg). Increased resorbed/dead fetuses (OR 1.84; 95% CI 1.27 to 2.66; SAR 20.26 W/kg), decreased fetal weight (SMD 0.31; 95% CI 0.15 to 0.48; SAR 9.83 W/kg) and length (SMD 0.45; 95% CI 0.07 to 0.83; SAR 4.55 W/kg), and increased malformations (including OR 3.22; 95% CI 1.9 to 5.46 for litters with malformed fetuses; SAR 16.63 W/kg) were reported. Delayed effects showed no association for brain weight (SMD 0.10; 95% CI -0.09 to 0.29) and learning/memory (SMD -0.54; 95% CI -1.24 to 0.17), but detrimental associations for motor activity (SMD 0.79; 95% CI 0.21 to 1.38) and motor/sensory functions (SMD -0.66; 95% CI -1.18 to -0.14); neurobehavioral meta-analyses were based on few studies from few laboratories.",
    "effect_direction": "mixed",
    "limitations": [
        "For most endpoints showing detrimental effects, certainty was rated low or very low.",
        "Neurobehavioural meta-analyses were based on few studies with limited independent replication (few laboratories).",
        "Limitations prevented assessment of effects at exposure levels below those eliciting a well-known adverse heating impact.",
        "Some analyses excluded studies rated at 'high concern' for risk of bias (OHAT), potentially limiting available evidence."
    ],
    "evidence_strength": "moderate",
    "confidence": 0.85999999999999998667732370449812151491641998291015625,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "RF-EMF",
        "radiofrequency electromagnetic field",
        "pregnancy",
        "in utero exposure",
        "non-human mammals",
        "experimental study",
        "systematic review",
        "meta-analysis",
        "SAR",
        "fetal weight",
        "fetal length",
        "malformations",
        "resorbed fetuses",
        "neurobehavioral outcomes",
        "OHAT",
        "GRADE"
    ],
    "suggested_hubs": [
        {
            "slug": "who-icnirp",
            "weight": 0.7800000000000000266453525910037569701671600341796875,
            "reason": "Abstract describes a WHO-coordinated international project and systematic review protocol for RF-EMF health effects."
        }
    ]
}

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AI-extracted fields are generated from the abstract/metadata and may be incomplete or incorrect. This content is for informational purposes only and is not medical advice.

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