Purpose of Investigation: To emphasize the importance of untreated thyrotoxicosis in pregnancy. When left untreated, severe maternal, fetal and even neonatal adverse outcomes such as preeclampsia, premature labor, low birthweight infants and increased perinatal mortality are prone to complicate the pregnancy. Presentation: A case of thyrotoxicosis untreated during pregnancy is reported. Conclusion: Many authors have concluded that there is no need for routine assessment of the thyroid hormones and TSH levels in pregnancy. Nonetheless laboratory assessment for thyrotoxicosis should be done in cases with suspicious symptoms and signs All thyrotoxic women should also be under treatment during pregnancy. Early diagnosis and/or control of hyperthyroidism would decrease the incidence of complications during pregnancy.