Graves' Disease in Two Pregnancies Complicated by Fetal Goitrous Hypothyroidism: Successful In Utero Treatment with Levothyroxine

Background: Treatment of Graves' disease during pregnancy with antithyroid drugs (ATDs) poses a risk of inducing hypothyroidism and, thus, development of a goiter to the fetus. Patient Findings: We report two patients referred to our department after discovery of a fetal goiter by ultrasound examination in the second trimester of pregnancy. The women receiving 400 mg/day propylthiouracil and 10 mg/day thiamizole, respectively, had thyrotropin and total thyroxine values within the normal reference range but a lowered free thyroxine level. Fetal blood sampling by cordocentesis revealed severe fetal hypothyroidism as the cause of goiter development. Reduction of maternal ATD dose and injection of levothyroxine intra-amniotically quickly reduced the goiter size, and both babies were born euthyroid and without goiters. Summary: Two pregnant women with Graves' disease were overtreated with ATDs inducing iatrogenic goiter in the fetuses. Successful treatment with intra-amniotic levothyroxine injections rendered the babies euthyroid and nongoitrous at birth. Conclusions: Correct interpretation of thyroid function tests during pregnancy in general-and during ATD therapy of Graves' disease in particular-is difficult. Awareness of pregnancy-related changes in maternal thyroid status, and a close teamwork among endocrinologists, obstetricians, and experts in fetal medicine, is pivotal in ensuring normal growth and development of the unborn child of these patients.