US NRC Medical Event Reports Related to Unplanned Dose to Fetus or Embryo, 2005-2024

We analyzed the US Nuclear Regulatory Commission event notifications related to unplanned exposure to fetus or embryo for events that occurred between 1 January 2005 and 31 December 2024. A total of 39 events were identified, 28 related to therapeutic and 11 to diagnostic nuclear medicine; no events related to brachytherapy or gamma teletherapy were found. The number of events fell during the study period (2005-2009: 15; 2020-2024: 6). The radioisotope in most (71.8 %) of the events was 131 I. A pregnancy test was performed in 21/28 therapy events and in 0/11 diagnostic events. The estimated age of the fetus ranged from 1 to 26 wk (mean 5.7 wk); in two therapy events, conception occurred after the administration of the radiopharmaceutical. The mean reported estimated dose to the fetus was 260 mSv (SD: 190; range 20-860) for the therapy events and 17 mSv (SD: 6; range 10-26) for the diagnostic events. Unplanned fetal exposures are occurring; for therapy events, the estimated dose to the fetus is often high enough that adverse effects are possible. We suggest institutions review their policies on patient consent and pregnancy testing.