Relapse of maternal thyrotoxicosis presenting as a second-trimester fetal goiter.

A large fetal goiter was detected at 22 weeks of gestation during an antenatal ultrasound scan of a woman with a previous history of Graves' disease treated by partial thyroidectomy. This unsuspected finding initiated maternal investigations and treatment. In untreated cases poor fetal outcome is common and unfortunately fetal thyrotoxicosis/thyroid enlargement frequently remains unrecognized in the first pregnancy. We report the case and its management and discuss the literature emphasizing the importance of screening for antibodies in the 'at-risk' women and the increasing importance of ultrasound in the evaluation and follow-up of these patients. Reports of thyrotoxic fetal goiters are extremely rare and, to our knowledge, there have been no previous reports of this in the second trimester.