Euthyroid or even hypothyroid pregnant women without antithyroid medication but with a history of treatment for thyrotoxicosis, almost always a subtotal strumectomy, may still produce thyroid-stimulating immunoglobulins. This can induce fetal and neonatal thyrotoxicosis. Without treatment this results in a high fetal and neonatal mortality and morbidity. Fetal treatment by administering antithyroid drugs during pregnancy improves this prognosis remarkably. A case is described, the literature is reviewed and guidelines for diagnosis and treatment are presented.