Case of radioactive iodine exposure during pregnancy

A 43-year-old woman (gravida 0, para 0) was diagnosed with thyroid carcinoma and had been receiving radioactive iodine for remnant ablation. Eventually, her pregnant status became apparent; during radiation, she was at 5 gestational weeks. She decided to continue the pregnancy and delivered a boy of 2362 g at 37 gestational weeks. The infant did not present thyroid dysfunction or developmental abnormalities at 2 months of age. The patient was in the early pregnancy stage during radiation, so the fetus did not develop radiation-related damage of the thyroid gland because at this stage, the fetal thyroid does not concentrate iodine. Although the mother had received radioactive iodine during the critical organogenesis period, the fetus did not develop teratogenicity because the radiation was administered at the borderline threshold for teratogenicity. This case suggests the importance of iodine thyroid absorption when considering radiation-related damage to the fetal thyroid gland during early pregnancy.