In utero diagnosis and treatment of fetal goitrous hypothyroidism, caused by maternal use of propylthiouracil

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Abstract
A fetal goitre is a potentially dangerous phenomenon because of mechanical obstruction and possible fetal thyroid function disorders. In this report we describe a patient with Graves' disease diagnosed in early pregnancy and treated with propylthiouracil, which resulted in a large fetal goitre and fetal hypothyroidism. The diagnostic problems are discussed and we focus on the need for fetal thyroid hormone serum evaluation. The only reliable way to obtain information about the fetal thyroid status is percutaneous fetal umbilical cord blood sampling, since amniotic fluid levels do not properly represent the fetal thyroid function. Fetal hypothyroidism can thus be diagnosed in utero and treated with intra‐amniotic injections of thyroxine. The recommended dose and frequency of injections are only based on a few case reports and for that reason we performed a second fetal blood sampling 1 week later to evaluate our therapy. Weekly intra‐amniotic injections of 250 μg of thyroxine seem to be sufficient to reduce a fetal goitre and give a normal thyroid hormone level.