REVIEW – March 2015

Ionizing radiation in radiological examination of pregnant patients

Authors: Martin Reim, Mare Lintrop, Pilvi Ilves

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The consensus statement of numerous international organisations (NCRP, ICRP, BEIR VII, CDC, ACR, ACOG) on the effects of ionizing radiation (IR) in the examination of pregnant patients is considered negligible at an exposed fetal dose of ≤50 mGy. The majority of diagnostic radiological modalities that use ionizing radiation (IR) remain under the dose of 50 mGy. According to the results of most studies, the teratogenic or mutagenic effects start from the threshold dose of 100-150 mGy. In diagnostic examinations where the gravid uterus is not directly exposed to IR the fetal absorbed dose is very low. The effects of IR depends also on the dose and on gestational age. There is correlation between higher dose and stronger effects while further gestational age results in lesser IR effects. The risks and benefits of any radiological examination should be considered from the maternal and fetal perspectives. Informed consent has to be documented in medical records. Modalities like sonography (US) and magnetic resonance imaging (MRI) do not make use of IR and will hence remain the first-line choices for pregnant patients. The MRI is considered safe practice starting from the 2nd trimester, but there are still some uncertainties about the possible risks for the developing fetus. For strong medical indications, the use of intravenous iodine and gadolinium based contrast media in the examination of pregnant patients is allowed but should be strictly limited. We should always keep in mind the principle of as low as reasonably achievable (ALARA), however, depending on medical circumstances the use of IR in the radiological examination of pregnant patients is not absolutely restricted.