Exposure to radioactive iodine-131 for scintigraphy or therapy does not preclude pregnancy in thyroid cancer patients

Radiation is known to be mutagenic. The aim of the present study was to ascertain whether exposure to 131I induces genetic damage, as assessed by pregnancy outcomes and the health status of offspring of women previously exposed to 131I during thyroid carcinoma treatment.

Data on 2113 pregnancies were obtained by interviewing female patients treated for thyroid carcinoma who had not received any significant external radiation to the ovaries.

The incidence of miscarriages was 11% before any treatment for thyroid cancer; this number increased slightly after surgery for thyroid cancer, both before (20%) and after (20%) 131I, but did not vary with the cumulative 131I dose. Miscarriages were more frequent (40%) in the ten women who were treated with 131I [mean dose: 3.8 GBq (108 mCi)] during the year preceding conception. Incidences of stillbirth, preterm birth, low birth weight, congenital malformation and death during the first year of life were not significantly different before or after 131I therapy. The incidence of thyroid disease and nonthyroidal malignancy was similar in children born either before or after their mothers were exposed to 131I.

With the exception of miscarriages, there is no evidence that exposure to radioiodine affects the outcome of subsequent pregnancies and offspring. The question of whether an increased incidence of miscarriages within 1 yr of 131I administration relates to gonadal irradiation or to insufficient control of hormonal thyroid status remains to be established.