Consequences of inadvertent radioiodine treatment of Graves' disease and thyroid cancer in undiagnosed pregnancy. Can we rely on routine pregnancy testing?

Introduction. Radioiodine and most cytostatic treatments are contraindicated in pregnancy. Still, inadvertent therapy does occur. Radioiodine was given to two pregnant women with Graves' disease and thyroid cancer respectively, both in their 20th gestational week. Routine pregnancy tests based on urinary -hCG had failed to indicate pregnancy in both cases. Methods. Estimation of doses to the foetuses and foetal thyroids. Scrutiny of pregnancy testing. Results and Conclusions. Doses to foetal thyroids were ablative (250-600 Gy). Total foetal dose in the Graves' patient was 100 mGy and compatible with survival, whereas a foetal dose of approximately 700 mGy together with induced hypothyroidism was fatal for the foetus of the cancer patient. Routine pregnancy tests may fail early and late in pregnancy. The possibility of pregnancy should be considered in all fertile women before therapy with radionuclides or cytostatic regimens, and a clinical investigation undertaken on wide indications with determination of serum -hCG, preferably together with an ultrasound examination.