Prenatal treatment of thyrotoxicosis to prevent intrauterine growth retardation.

A woman with hypothyroidism and Graves ophthalmopathy was treated with propylthiouracil during her second pregnancy. This was employed because her first pregnancy resulted in an infant with severe intrauterine growth retardation and neonatal thyrotoxicosis. The antithyroid drug used during the second pregnancy crossed the placenta and treated the infant in utero. The infant was delivered by elective cesarean section at 36 weeks and was a live-born male with appropriate height and weight without evidence of thyrotoxicosis. The therapeutic benefit of propylthiouracil during this second pregnancy seems likely, based on the development of neonatal thyrotoxicosis after 4 days of life and on the presence of high thyroid-stimulating immunoglobulin levels in the mother and the infant.