Impact of repetitive exposure to strong static magnetic fields on pregnancy and embryonic development of mice

Survey of Delivery Outcomes for Employees at MR Imaging Facilities in Japan Based on Information Recorded in the Maternal and Child Health Handbook

The effect of maternal occupational non-ionizing radiation (NIR) exposure from MRI on premature birth and low birth weight delivery was analyzed based on questionnaire survey (263 employees, 443 births). Although the highest occurrence rates of both outcomes were observed in the group whose NIR exposure occurred only before pregnancy, no statistical significance was detected.

11.4 T ultra-high static magnetic field has no effect on morphology but induces upregulation of TNF signaling pathway based on transcriptome analysis in zebrafish embryos

As magnetic resonance imaging (MRI) scanners with ultra-high field (UHF) have optimal performance, scientists have been working to develop high-performance devices with strong magnetic fields to improve their diagnostic potential. However, whether an MRI scanner with UHF poses a risk to the safety of the organism require further evaluation. This study evaluated the effects of 11.4 Tesla (T) UHF on embryonic development using a zebrafish model. Multiple approaches, including morphological parameters, physiological behaviors, and analyses of the transcriptome at the molecular level, were determined during 5 days after laboratory-controlled exposure from 6 hour post fertilization (hpf) to 24 hpf. No significant effects were observed in embryo mortality, hatching rate, body length, Left-Right patterning, locomotor behavior, etc. RNA-sequencing analysis revealed up-regulated tumor necrosis factor (TNF) inflammatory factors and activated TNF signaling pathways in the 11.4 T exposure group. The results were further validated using qPCR. Our findings indicate that although UHF exposure under 11.4 T has no effect on the development of zebrafish embryos, it has specific effects on the immune response that require further investigation.

No Meta-Analytic Evidence for Risks due to Prenatal MRI in Animal Models

BACKGROUND

Magnetic resonance imaging (MRI) is a powerful, non-invasive tool for both clinical practice and research. Though the safety of MRI has been endorsed by many professional societies and government bodies, some concerns have remained about potential risk from prenatal MRI. Case-control animal studies of MRI scanning during gestation and effects on offspring are the most direct test available for potential risks. Herein, we provide a meta-analysis of extant animal studies of prenatal MRI examining reproductive and offspring outcomes.

METHODS

Relevant articles were identified through PubMed search and citation searching of known articles and review papers. Eighteen relevant studies were identified with case-control designs of prenatal scanning conducted in vivo with mammalian species using MRI-relevant field strength. Standardized mean difference effect sizes were analyzed across k=81 outcomes assessed across n=649 unexposed dams, n=622 exposed dams, n=3031 unexposed offspring, n=3378 exposed offspring, using a multi-level meta-analysis approach that clustered effect sizes within publication.

RESULTS

The meta-analysis indicated no significant evidence for an effect of prenatal MRI (SMD=0.17, 95% CI=[-0.19,0.54], t=0.94, p=.35) across outcomes. Similarly, no effects were observed when separately examining the four most commonly assessed outcomes: birth weight, litter size, fetal viability, and physical malformations (p>.05).

CONCLUSIONS

Case-control mammalian animal studies indicate no significant known risks of prenatal MRI to reproductive outcomes or offspring development. This is largely mirrored in human research, though the lack of randomized case-control designs limits direct comparison. The current findings provide additional support to the prevailing consensus that prenatal MRI poses no known risk to offspring.

Depolarization imaging for fast and non-invasive monitoring of cervical microstructure remodeling in vivo during pregnancy

The cervix plays a crucial role in conception, maintenance of pregnancy, and childbirth. The mechanical properties of a pregnant woman's cervix change dramatically during gestation due to a remodeling of its microstructure, necessary for delivery. However, external factors can accelerate this process and lead to prematurity, the primary cause of perinatal mortality worldwide, due to the inefficiency of existing diagnostic methods. This study shows that polarized light is a powerful tool to probe the cervical microstructure during pregnancy. A wide-field multispectral polarimetric imaging system was fabricated to explore in vivo the cervix of full-term pregnant women. The polarimetric properties of the cervix change significantly with pregnancy progression. In particular, a set of several depolarization parameters (intrinsic and extrinsic) showed a strong linear correlation with gestational age in the red part of the visible spectral range. This trend can be attributed, among other things, to a decrease in collagen density and an increase in hydration of cervical connective tissue. Wide field depolarization imaging is a very promising tool for rapid and non-invasive analysis of cervical tissue in vivo to monitor the steady progression of pregnancy, providing the practitioner with useful information to improve the detection of preterm birth.

Effects of Moderate to High Static Magnetic Fields on Reproduction

With the wide application of magnetic resonance imaging in hospitals and permanent magnets in household items, people have increased exposure to various types of static magnetic fields (SMFs) with moderate and high intensities, which has caused a considerable amount of public concern. Studies have shown that some aspects of gametogenesis and early embryonic development can be significantly affected by SMFs, while others have shown no effects. This review summarizes the experimental results of moderate to high-intensity SMFs (1 mT-16.7 T) on the reproductive development of different model animals, and we find that the effects of SMFs are variable depending on experimental conditions. In general, the effects of inhomogeneous SMFs seem to be more significant compared to that of homogeneous SMFs, which is likely due to magnetic forces generated by the magnetic field gradient. Moreover, some electromagnetic fields may have induced bioeffects because of nonnegligible gradient and heat effect, which are much reduced in superconducting magnets. We hope this review can provide a starting point for more in-depth analysis of various SMFs on reproduction, which is indispensable for evaluating the safety and potential applications of SMFs on living organisms in the future. © 2022 Bioelectromagnetics Society.

The Effects of Anthropogenic Electromagnetic Fields (EMF) on the Early Development of Two Commercially Important Crustaceans, European Lobster, Homarus gammarus (L.) and Edible Crab, Cancer pagurus (L.)

Proposed offshore windfarm sites could overlap with the brooding and spawning habitats of commercially important crustacea, including European lobster, Homarus gammarus and Edible crab, Cancer pagurus. Concerns have been raised on the biological effects of Electromagnetic Fields (EMFs) emitted from subsea power cables on the early life history of these species. In this study, ovigerous female H. gammarus and C. pagurus were exposed to static (Direct Current, DC) EMFs (2.8 mT) throughout embryonic development. Embryonic and larval parameters, deformities, and vertical swimming speed of freshly hatched stage I lobster and zoea I crab larvae were assessed. EMF did not alter embryonic development time, larval release time, or vertical swimming speed for either species. Chronic exposure to 2.8 mT EMF throughout embryonic development resulted in significant differences in stage-specific egg volume and resulted in stage I lobster and zoea I crab larvae exhibiting decreased carapace height, total length, and maximum eye diameter. An increased occurrence of larval deformities was observed in addition to reduced swimming test success rate amongst lobster larvae. These traits may ultimately affect larval mortality, recruitment and dispersal. This study increases our understanding on the effects of anthropogenic, static EMFs on crustacean developmental biology and suggests that EMF emissions from subsea power cables could have a measurable impact on the early life history and consequently the population dynamics of H. gammarus and C. pagurus.

What to Expect When Expecting in Lab: A Review of Unique Risks and Resources for Pregnant Researchers in the Chemical Laboratory

Pregnancy presents a unique risk to chemical researchers due to their occupational exposures to chemical, equipment, and physical hazards in chemical research laboratories across science, engineering, and technology disciplines. Understanding “risk” as a function of hazard, exposure, and vulnerability, this review aims to critically examine the state of the science for the risks and associated recommendations (or lack thereof) for pregnant researchers in chemical laboratories (labs). Commonly encountered hazards for pregnant lab workers include chemical hazards (organic solvents, heavy metals, engineered nanomaterials, and endocrine disruptors), radiation hazards (ionizing radiation producing equipment and materials and nonionizing radiation producing equipment), and other hazards related to the lab environment (excessive noise, excessive heat, psychosocial stress, strenuous physical work, and/or abnormal working hours). Lab relevant doses and routes of exposure in the chemical lab environment along with literature and governmental recommendations or resources for exposure mitigation are critically assessed. The specific windows of vulnerability based on stage of pregnancy are described for each hazard, if available. Finally, policy gaps for further scientific research are detailed to enhance future guidance to protect pregnant lab workers.

Strong static magnetic field delayed the early development of zebrafish

One of the major topics in magnetobiology is the biological effects of strong static magnetic field (SMF) on living organisms. However, there has been a paucity of the comprehensive study of the long-term effects of strong SMF on an animal's development. Here, we explored this question with zebrafish, an excellent model organism for developmental study. In our research, zebrafish eggs, just after fertilization, were exposed to a 9.0 T SMF for 24 h, the critical period of post-fertilization development from cleavage to segmentation. The effects of strong SMF exposure on the following developmental progress of zebrafish were studied until 6 days post-fertilization (dpf). Results showed that 9.0 T SMF exposure did not influence the survival or the general developmental scenario of zebrafish embryos. However, it slowed down the developmental pace of the whole animal, and the late developers would catch up with their control peers after the SMF was removed. We proposed a mechanical model and deduced that the development delaying effect was caused by the interference of SMF in microtubule and spindle positioning during mitosis, especially in early cleavages. Our research data provide insights into how strong SMF influences the developing organisms through basic physical interactions with intracellular macromolecules.

Safety of exposure to high static magnetic fields (2 T-12 T): a study on mice

OBJECTIVES

We aimed to evaluate the biological effects of high static magnetic field (HiSMF, 2-12 Tesla [T]) exposure on mice in a stable and effective breeding environment in the chamber of a superconducting magnet.

METHODS

C57BL/6 mice were bred in the geomagnetic field and HiSMF with different magnetic field strengths (2-4 T, 6-8 T, and 10-12 T) for 28 days. The body weight, blood indices, organ coefficients, and histomorphology of major organs were analyzed.

RESULTS

The results showed that the HiSMF had no significant effect on the body weight, organ coefficients, or histomorphology of major organs in mice. The HiSMF had no effect on most routine blood and biochemical indices, but the value of the mean corpuscular hemoglobin (MCH) was increased in the 2-4 T group compared with that of the other groups, and the uric acid level (UA) was decreased in the three HiSMF groups compared with that of the control group.

CONCLUSION

The C57BL/6 mice were not affected when they were exposed to different HiSMF environments for 28 days.

KEY POINTS

• No physiological problems were observed in mice with long-term whole-body exposure to HiSMF.

The Effects of Enriched Environmental Intervention on the Parturition Outcome and Filial Health of Pregnant Mice With Chronic Pain

Chronic pain (CP) adversely impacts people's health. However, the influence of CP on pregnant women and their fetuses remains unclear. Few reasonable interventions have been offered to these women. This study aimed to examine the effects of enriched environmental intervention (EEI) on the delivery outcome and offspring health of pregnant mice with CP. Forty pregnant mice were equally and randomly divided into four groups (control, sham, CP, and CP + EEI). Monoarthritis was induced by subcutaneous injection of the complete Freund's adjuvant (100 μg/100 μl) into the left hind paw of mice on Day 0 of gestation. Sham mice received 100 µl of sterile phosphate-buffered saline subcutaneously. General health status and delivery outcomes of pregnant mice and general physical status, growth, and development of offspring were observed and compared between groups. CP mice exhibited less weight gain, higher rate of premature delivery, smaller litter size, lower live birth rate, lower filial birth weight, shorter filial tail length, and lower filial rates of achieving righting reflex and crawling compared to mice in the control/sham/CP + EEI groups. There were no significant differences between mice in the CP + EEI group and those in the control and sham groups. CP during pregnancy led to serious adverse impacts on both the mother and fetus mice in this study, and EEI was an effective treatment for these effects.