Fetal blood sampling in the management of intrauterine thyrotoxicosis

Graves disease is an autoimmune disorder caused by thyroid-stimulating immunoglobulins (Igs) which result in an excess production of thyroid hormones. These Igs are passively transferred to the fetus and may produce intrauterine thyrotoxicosis. Thyrotoxic fetuses are at risk for preterm delivery, intrauterine growth retardation, and perinatal death. Our patient had markedly elevated thyroid-stimulating Igs and had given birth to a preterm thyrotoxic infant in a previous pregnancy. We managed her third pregnancy with serial assessment of fetal thyroid hormones by funipuncture to identify the hyperthyroid fetus and modulate propylthiouracil therapy. We believe that this approach in selected patients with Graves disease may improve the outcome of these pregnancies.