[Isolated fetal tachycardia, a diagnostic event of Basedow's disease. Apropos of a case].

Two of thousand pregnancies are complicated by a Graves' disease. The circumstances of diagnosis are usually maternal disorders (tachycardia, exophthalmia, loss of weight...), also fetal disorders (tachycardia, intra-uterine growth retardation, stillborn...). The discovery of fetal tachycardia (160 beats per minute), and maternal tachycardia (120 beats per minute) associated with high blood pressure, allowed us to suspect, in this case, a Graves' disease, responsible of fetal hyperthyroidism by autoantibodies crossing the placenta. The measuring of T3, T4, TSH and autoantibodies confirmed the diagnosis. The drug of choice is the PTU (propylthiouracil). It prevents synthesis of thyroid hormones and inhibits peripheral deiodination of T4 to T3. It treats simultaneously mother and fetus; the surveillance must allow us to adjust treatment to avoid fetal hypothyroidism, maternal thyrotoxicosis of peripartum and neonatal thyrotoxicosis.