All women, teens and older women included, must have a pregnancy test before the administration of any treatment dose of radioiodine: eg, for thyroid cancer or Graves' disease. Administration of radioactive iodine to a pregnant woman can cause destruction of the fetus' thyroid.

Women receiving therapy with radioactive iodinne are cautioned against starting a pregnancy for at least 4 months following treatment. Men receiving radioiodine have an increased number of abnormal sperm visible for several months and should avoid starting a pregnancy for at least 6 months after treatment. Observations on the children of women who have had prior radioiodine treatment have shown that their babies do not have problems at any higher rate than the general population.