Fetal radiation exposure: Is monitoring really needed?

A historical review of the effects of dental radiography on pregnant patients

BACKGROUND

The safety of dental radiography performed on pregnant patients has been a controversial topic since the 1960s. This review synthesizes and consolidates findings, from 1957 through 2021, of the effects dental ionizing radiation could have on a pregnant patient and in utero birth defects.

TYPES OF STUDIES REVIEWED

Using PubMed, the following key words were searched: pregnancy, radiology, radiograph, radiation dose, fetus, x-ray, and dental. Criteria evaluation was done on the basis of availability, completeness, quality, relevance, technicality (that is, dental radiography), topicality (that is, pregnant patients), and usability. These results were then filtered on the basis of quantitative and qualitative data as well as the period (decades within the historical framework). The final selection of relevant literature consisted of various studies including cohort studies, systematic reviews, meta-analyses, case reports, and other narrative reviews.

RESULTS

If properly performed, the amount of ionizing radiation produced during dental radiographic procedures is so low that it is unlikely to reach the teratogenic threshold. Thus, dental ionizing radiation is unlikely to cause in utero birth defects because it has been detected to have a deterministic (not stochastic) effect. With this information and historical context, this article shows that necessary dental radiography is safe at any stage during pregnancy, as long as proper safety equipment is appropriately used.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

As technology advances, more research can further clarify ionizing radiation safety for pregnant patients and its potential effects on in utero birth defects, improving overall oral health care. The dental community must remain educated about current ionizing radiation safety guidelines to make better-informed decisions and successfully provide proper oral health care to pregnant patients.

Prenatal Radiation Exposure Leads to Higher-Order Telencephalic Dysfunctions in Adult Mice That Coincide with Reduced Synaptic Plasticity and Cerebral Hypersynchrony

Higher-order telencephalic circuitry has been suggested to be especially vulnerable to irradiation or other developmentally toxic impact. This report details the adult effects of prenatal irradiation at a sensitive time point on clinically relevant brain functions controlled by telencephalic regions, hippocampus (HPC), and prefrontal cortex (PFC). Pregnant C57Bl6/J mice were whole-body irradiated at embryonic day 11 (start of neurogenesis) with X-ray intensities of 0.0, 0.5, or 1.0 Gy. Female offspring completed a broad test battery of HPC-/PFC-controlled tasks that included cognitive performance, fear extinction, exploratory, and depression-like behaviors. We examined neural functions that are mechanistically related to these behavioral and cognitive changes, such as hippocampal field potentials and long-term potentiation, functional brain connectivity (by resting-state functional magnetic resonance imaging), and expression of HPC vesicular neurotransmitter transporters (by immunohistochemical quantification). Prenatally exposed mice displayed several higher-order dysfunctions, such as decreased nychthemeral activity, working memory defects, delayed extinction of threat-evoked response suppression as well as indications of perseverative behavior. Electrophysiological examination indicated impaired hippocampal synaptic plasticity. Prenatal irradiation also induced cerebral hypersynchrony and increased the number of glutamatergic HPC terminals. These changes in brain connectivity and plasticity could mechanistically underlie the irradiation-induced defects in higher telencephalic functions.

Efficacy and safety of endoscopic retrograde cholangiopancreatography in pregnancy: A high-volume study with long-term follow-up

BACKGROUND/AIMS

Pancreaticobiliary diseases are observed more frequently in pregnancy due to increased biliary stone formation. There are some concerns about the use of endoscopic retrograde cholangiopancreatography (ERCP) because of potential fetal exposure to radiation and serious adverse events, such as post-ERCP pancreatitis, which increases fetal or maternal morbidity and mortality. The aim of this study was to evaluate the efficacy and safety of ERCP during pregnancy and to present our experience.

MATERIALS AND METHODS

This study included 25 pregnant patients who underwent ERCP due to biliopancreatic pathologies between 2010 and 2017. Indications for ERCP were choledocholithiasis (n=12), biliary pancreatitis (n=9), and acute cholangitis (n=4). ERCP procedures were performed using fluoroscopy (n=18) and the non-radiation technique (n=7). The duration of fluoroscopy was recorded in all cases. Fetal and maternal complications were both assessed.

RESULTS

The mean age of patients was 29.4 (range, 21-40) years, and the mean duration of pregnancy was 19.9 weeks. All the 25 ERCP procedures were performed successfully. Biliary sphincterotomy was performed in all patients, and 18 patients with choledocholithiasis underwent stone extraction. The average procedure duration was 11 min, and the average duration of fluoroscopy was 6 s. There were no major complications in any patient. After the deliveries, the newborns were apparently healthy during the follow-up period of 1-7 years.

CONCLUSION

Either conventional or non-radiation ERCP procedures can be performed successfully in pregnancy, with no increase in the number of feto-maternal complications when performed by experienced endoscopists.

A multidisciplinary approach unravels early and persistent effects of X-ray exposure at the onset of prenatal neurogenesis

Background

In humans, in utero exposure to ionising radiation results in an increased prevalence of neurological aberrations, such as small head size, mental retardation and decreased IQ levels. Yet, the association between early damaging events and long-term neuronal anomalies remains largely elusive.

Methods

Mice were exposed to different X-ray doses, ranging between 0.0 and 1.0 Gy, at embryonic days (E) 10, 11 or 12 and subjected to behavioural tests at 12 weeks of age. Underlying mechanisms of irradiation at E11 were further unravelled using magnetic resonance imaging (MRI) and spectroscopy, diffusion tensor imaging, gene expression profiling, histology and immunohistochemistry.

Results

Irradiation at the onset of neurogenesis elicited behavioural changes in young adult mice, dependent on the timing of exposure. As locomotor behaviour and hippocampal-dependent spatial learning and memory were most particularly affected after irradiation at E11 with 1.0 Gy, this condition was used for further mechanistic analyses, focusing on the cerebral cortex and hippocampus. A classical p53-mediated apoptotic response was found shortly after exposure. Strikingly, in the neocortex, the majority of apoptotic and microglial cells were residing in the outer layer at 24 h after irradiation, suggesting cell death occurrence in differentiating neurons rather than proliferating cells. Furthermore, total brain volume, cortical thickness and ventricle size were decreased in the irradiated embryos. At 40 weeks of age, MRI showed that the ventricles were enlarged whereas N-acetyl aspartate concentrations and functional anisotropy were reduced in the cortex of the irradiated animals, indicating a decrease in neuronal cell number and persistent neuroinflammation. Finally, in the hippocampus, we revealed a reduction in general neurogenic proliferation and in the amount of Sox2-positive precursors after radiation exposure, although only at a juvenile age.

Conclusions

Our findings provide evidence for a radiation-induced disruption of mouse brain development, resulting in behavioural differences. We propose that alterations in cortical morphology and juvenile hippocampal neurogenesis might both contribute to the observed aberrant behaviour. Furthermore, our results challenge the generally assumed view of a higher radiosensitivity in dividing cells. Overall, this study offers new insights into irradiation-dependent effects in the embryonic brain, of relevance for the neurodevelopmental and radiobiological field.

Electronic supplementary material

The online version of this article (doi:10.1186/1866-1955-7-3) contains supplementary material, which is available to authorized users.