Background: Autoimmune GD (Graves' Disease) is the most common cause of hyperthyroidism in women of childbearing age. To prevent maternal and fetal complications, thyrotoxicosis during pregnancy should be adequately managed and controlled. The physiological adaptations associated with pregnancy challenge the assessment of thyroid function in pregnant women, and the treatment with antithyroid drugs (ATD) raises concerns for the pregnant woman and the fetus. Our aim of this study was to discuss the effect of hyperthyroidism on pregnancy, different methods of diagnosis of hyperthyroidism and treatment of hyperthyroidism during pregnancy for a favorable maternal health and fetal outcome. Objective: To discuss thyrotoxicosis this affects the pregnant woman and the effect of hyperthyroidism on pregnancy. It is to discuss different methods of diagnosis of hyperthyroidism during pregnancy. Also it is to study the treatment of hyperthyroidism and thyrotoxicosis during pregnancy for a favorable maternal health and fetal outcome. Patients and Methods: A prospective randomized clinical study that was conducted on 20 pregnant female patients with thyrotoxicosis in different stages of pregnancy attending Bab-El Shaaria and El-Hussein University Hospitals through the period from April (2020) to December (2020). The selected patients received one of the two main medications which are propyl-thiouracil (PTU) and methimazole (MMI). Propylthiouracil was given in the 1st trimester and Methimazole was given in 2nd and 3rd trimester. Results: There was statistically significant difference found between pretreatment and post treatment groups regarding Heat Intolerance, Palpitations, Tremors, and Irritability, while there was no statistically significant difference found between Pretreatment and Post treatment regarding Exophthalmos. Methimazole (MMI) is preferred to propyl-thiouracil (PTU) after the first trimester because PTU has an association with hepatotoxicity. However, PTU is recommended for the first trimester of pregnancy because its teratogenic effects are considered less severe than those of MMI. Conclusion: Management of hyperthyroidism during pregnancy and lactation requires special considerations and should be meticulously implemented to provide best care to pregnant woman and prevent any adverse effects. Thyrotoxicosis of pregnancy can present unique diagnostic challenges and, if untreated, is associated with increased risks of adverse maternal, fetal, and neonatal complications. The clinical presentation, serum thyroid function test results, and serum TRAb titers can help differentiate the etiology of thyrotoxicosis. However, assessment and monitoring with serum thyroid function tests can be difficult, as there is significant overlap between test results arising from normal pregnancy physiology and intrinsic hyperthyroidism.