BACKGROUND: Uncontrolled thyroid dysfunction in pregnancy is associated with adverse fetal and maternal outcomes. OBJECTIVES: To review relevant literature and developments in the medical management of thyroid dysfunction in pregnancy. RESULTS: Hyperthyroidism in pregnancy requires careful control of maternal disease whilst avoiding fetal hypothyroidism. Propylthiouracil is the preferred antithyroid drug in pregnancy although thiamazole can be used where propylthiouracil is unavailable. Synthetic levothyroxine is the treatment of choice in hypothyroidism. Patients with pre-existing hypothyroidism will generally require an increase in thyroxine dose in pregnancy. Most patients with postpartum thyroiditis will require treatment during the hypothyroid phase. Long-term follow-up of patients with this syndrome is essential owing to the risk of permanent hypothyroidism. CONCLUSION: Excellent maternal and fetal outcomes can be achieved with appropriate management of thyroid dysfunction in pregnancy.