The prevalence of hyperthyroidism in pregnancy is about 0.2%. The most common cause is Graves' disease. Maternal, fetal, and neonatal morbidity and mortality may be reduced to a minimum with careful attention to the clinical symptoms and interpretation of thyroid tests. Ideally, hyperthyroid women should be rendered euthyroid before considering conception. The incidence of maternal and neonatal morbidity is significantly higher in those patients whose hyperthyroidism is not medically controlled. Even the incidence of thyroid storm is high in women who are under poor medical supervision in the presence of a medical or obstetric complication. Maternal morbidity includes a higher incidence of toxemia, premature delivery, placenta abruptio, congestive heart failure, and thyroid crisis. In some series, anemia and infections were also reported. Neonatal morbidity includes SGA neonates, intrauterine growth retardation, LBW infants, and prematurity. Fetal goiter and transient neonatal hypothyroidism is occasionally reported in infants of mothers who have been overtreated with ATD. Propylthiouracil and MMI are equally effective in controlling the disease. In most patients, symptoms improved and thyroid tests returned to normal in 3-8 weeks after initiation of therapy. Resistance to ATD is extremely rare, most cases are caused by patient poor compliance. Surgery for the treatment of hyperthyroidism is reserved for the unusual patient who is allergic to both ATD; to those who have large goiters; to those who require large doses of ATD; or to those patients who poorly comply. Fetal and neonatal hyperthyroidism can be predicted in the majority of cases by the previous maternal medical and obstetric history and by the proper interpretation of thyroid tests. Finally, hyperthyroidism may recur in the postpartum period.