Three fertile female patients aged 33, 29 and 38 years, respectively, were treated with radioiodine 1-131 for Graves' disease. In retrospect, the first woman was 14 weeks pregnant at the time of treatment, and the other 2 women were treated around the time of conception. All 3 women decided to continue their pregnancies after being counselled about the potential adverse health risks of radioiodine therapy for the infant. The first woman was delivered at term of an infant diagnosed with hypothyroidism that was ascribed to radioiodine. The other 2 women delivered euthyroid infants. According to international standards, radioiodine should not be given during pregnancy because of its toxic effects. An interval of at least 4 months is advised between maternal radioiodine therapy and conception. This should be discussed with the patient. Prior to the initiation of radioiodine therapy, menstrual and contraceptive history should be ascertained in fertile female patients. Pregnancy testing should be performed where indicated, and the result should be verified before radioiodine therapy is initiated.