Although radioactive iodine treatments are generally safe, they can't be given to pregnant women because the chemical may destroy the thyroid gland in the fetus. So you must make sure you're not pregnant before you take radioactive iodine for Graves' disease. It's best to let several months pass after your last dose of radioactive iodine before becoming pregnant. Talk to your doctor about how long you should wait. Except during the time right after treatment, radioactive iodine poses no health risks for women who want to become pregnant. It won't affect the fertility of women or men.