Antenatal diagnosis and treatment of fetal hypothyroidism. A report of two cases.

Fetal goiter in the presence of maternal Graves' disease can signify either hyperthyroidism or hypothyroidism in the fetus. Two patients with Graves' disease taking propylthiouracil were found to have a fetal goiter on a prenatal sonogram. Fetal blood sampling identified hypothyroidism in both instances. Administration of intraamniotic thyroxine resulted in rapid resolution of the goiter, normalization of subsequent fetal thyroid studies, and delivery of a euthyroid fetus. Cordocentesis allows accurate diagnosis and follow-up of fetal thyroid dysfunction and prompt initiation of appropriate therapy.