Advances in prenatal imaging techniques and in fetal hormonology now allow for identification of disorders of thyroid function in the fetus. These can potentially be treated in utero by giving drugs to the mother. This review shows the feasibility of in utero treatment of fetal thyroid disorders, either indirectly by treating the mother or by giving the necessary drugs directly to the fetus. For goitrous fetal hypothyroidism leading to hydramnios, repeated intra-amniotic injections of thyroxine have been reported to decrease the size of the fetal thyroid. Experience with such procedures is limited but positive. The risk that direct in utero treatment of the fetus may provoke premature labor or cause infection should be carefully evaluated. In women with Graves' disease, autoimmune fetal hyperthyroidism can generally be treated in a noninvasive way by optimizing treatment of the mother, such as by increasing the dose of antithyroid drugs. Follow-up of the efficacy and the possible long-term consequences of medical interventions to normalize thyroid function of the fetus are of great importance. Specialized care of the fetus should be provided by skilled teams with extensive experience in prenatal care.