Outcome of pregnancy after radioactive iodine treatment for well differentiated thyroid carcinomas

This study sought to determine the outcome of pregnancy in female patients with differentiated thyroid carcinoma who became pregnant after radioactive iodide treatment. A total of 779 female thyroid cancer patients were treated at Chang Gung Medical Center in Linkou between January 1977 and December 1995. The medical records of these patients were reviewed retrospectively. Thirty-seven of these patients had well differentiated thyroid carcinoma receiving 131I treatment and conceived at a mean age of 27.97 ± 3.49 year-old. A total of 58 pregnancy episodes were recorded during this study period. Among these 37 patients, 3 episodes of artificial abortion, 8 episodes of spontaneous abortion and 2 threatened abortions were observed. These patients delivered a total of 47 babies including 3 premature babies. Seven of these patients conceived within 6 months after the last administration of 131I, including 2 cases within 1 month, 4 cases within 4 months, and 1 patient within 5 months. Of these 7 patients, only one patient who conceived within 6 months after the last administration of 131I (14.3%) had a spontaneous abortion. The present results suggest that previous administration of 131I in female patients with well differentiated thyroid cancer does not result in demonstrable adverse effects in subsequent pregnancies. However, further studies involving long-term follow-up of children delivered by mothers who became pregnant within 6 months after the last administration of 131I is needed to further elucidate the possible chronic effects and sequelae of 131I therapy on subsequent pregnancies.