Introduction: Nuclear medicine uses radiopharmaceuticals that emit ionizing radiation.
During pregnancy, these procedures are performed only when the benefit for the mother and
the fetus outweigh the potential risk. Due to increased radiosensitivity, the fetus is
particularly vulnerable, therefore it is important to evaluate the transfer and biokinetics of
radiopharmaceuticals as well as the fetal radiation dose. The risk to the fetus depends on
gestational age, the type of radiopharmaceutical used, and the amount of radiation received
during the examination. Purpose: The aim of this thesis is to examine the effects of
radiopharmaceuticals on the fetus during pregnancy and to describe their justified use,
possible effects on the fetus, and the period of greatest sensitivity to ionizing radiation
through a systematic literature review. Methods: A descriptive method with a systematic
literature review was used. Literature was searched in international databases such as
PubMed, ScienceDirect, Wiley Online Library, Google Scholar, and the European Journal
of Medical Physics. Articles published between 2010 and 2026 in English were included.
The following keywords were used: pregnant women, pregnancy, fetus, fetal dose,
radiopharmaceuticals, nuclear medicine, and molecular imaging. In the analysis, we
considered the methods, results, and findings related to fetal dose, safe use of
radiopharmaceuticals, and risk-reduction measures. Results: After reviewing the databases,
12 relevant articles were included in the analysis. Their methods, results, and findings
regarding fetal dose, fetal sensitivity, and the safe use of radiopharmaceuticals were
examined. The findings show that the fetus is most sensitive during the first trimester, that
most commonly used radiopharmaceuticals result in low doses below the threshold for
deterministic effects, and that appropriate measures such as reduced administered activity,
hydration, and frequent urination can further reduce the risk. Discussion and
conclusion: We found that the fetus is most sensitive to ionizing radiation in early
pregnancy, particularly during organogenesis. The average fetal doses in standard diagnostic
procedures, such as positron emission tomography combined with computed tomography
using 18fluorine fluorodeoxyglucose or scintigraphy with 99m-technetium, remain low and
do not exceed the thresholds for deterministic effects. The use of radiopharmaceuticals is
justified only when the diagnostic outcome directly affects the mother’s treatment. In such
cases, it is essential to follow the principle of keeping radiation exposure as low as
reasonably achievable, optimize protocols, reduce the administered activity, and encourage
hydration and frequent bladder emptying. The most commonly used diagnostic
radiopharmaceuticals are 99m-technetium compounds and 18fluorine fluorodeoxyglucose,
whereas therapeutic use of radiopharmaceuticals, especially 131iodine, is almost always
discouraged during pregnancy. Properly planned use of radiopharmaceuticals during
pregnancy can therefore be safe and can provide diagnostic benefit with minimal risk to the
fetus.
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