Fetal thyrotoxicosis associated with nonimmune hydrops.

The reported manifestations of thyrotoxicosis in the fetus include tachycardia, preterm birth, intrauterine growth retardation, and increased perinatal mortality. Presented is a twin pregnancy in a euthyroid mother with a history of Graves' disease and high levels of thyroid-stimulating immunoglobulin G antibodies, which resulted in nonimmune hydrops in one of the twins.