Conception after Iodine-131 Therapy for Differentiated Thyroid Cancer

Abstract

We reviewed the medical history of 26 women with differentiated thyroid cancer who became pregnant after receiving therapeutic doses of radioactive iodine (131I) in order to document the possibility of a greater risk for disorders in these pregnancies. There were a total of 39 pregnancies, 6 of which occurred during the first year after therapy. In 3 cases the following anomalies were encountered: a male suffering Trisomy 18 (Edward's syndrome), a female with constitutional aplastic anemia, and a male with a congenital hip dysplasia. Of the 33 pregnancies that occurred after the first year post-therapy, there were 2 spontaneous abortions and a male effected by ureteral stenosis. Based on these data, although it cannot be confirmed that these congenital disorders are due to the 131I therapy, we recommend that pregnancy be avoided for the first year after therapy.

Guidelines for the management of thyroid cancer

“…Exposure of the foetus to radiation is potentially harmful . A small risk of spontaneous abortion may persist for up to 1 year after high‐dose 131 I remnant ablation (RRA) or therapy and this may relate to suboptimal thyroid hormonal control . The possible deleterious effects of radiation on gonadal function and the outcome of subsequent pregnancies have been reviewed .…”

Thyroid Medications During Pregnancy

“…127 The outcome depends on the gestational age at which exposure occurs. 133 Other studies show no increased incidence of deleterious effects, particularly if conception was delayed for 1 year after treatment. 127 Congenital hypothyroidism has been reported in offspring of mothers who received therapeutic doses of radioiodine.…”

“…127 Congenital hypothyroidism has been reported in offspring of mothers who received therapeutic doses of radioiodine. 128,133,134 130 Potential therapies to attempt alleviation of these outcomes would include administration of cold iodine to lower fetal radioiodine uptake, and use of LT 4 , delivered to the mother or to the amniotic fluid, to treat fetal hypothyroidism.…”

Radioactive iodine (131I) effects on male fertility

“…The preliminary finding of an increased number of miscarriages in pregnancies, starting within 1 year after treatment with high 131 I dose [28] was not confirmed when the case series was further extended by the same authors [29]. In these cases, the role of ovarian irradiation is not determined [26,30]. In these cases, the role of ovarian irradiation is not determined [26,30].…”