The relationship between maternal serum thyroid-stimulating immunoglobulin and fetal and neonatal thyrotoxicosis

OBJECTIVE: To estimate whether the risk of neonatal thyrotoxicosis was related to the value of maternal thyroid-stimulating immunoglobulin in women with Graves disease. METHODS: The records of pregnant women undergoing testing for thyroid-stimulating immunoglobulin over a 10-year period were analyzed. Neonatal thyrotoxicosis was defined as the presence of tachycardia, goiter, hydrops, tremulousness, voracious appetite, irritability, cardiomegaly, or congestive heart failure, with elevated thyroid hormone levels. The relationship between maternal thyroid-stimulating immunoglobulin values and the development of thyrotoxicosis was examined. The sensitivity, specificity, and positive and negative predictive values were calculated using an arbitrarily chosen cutoff for thyroid-stimulating immunoglobulin. RESULTS: Twenty-nine women with a history of Graves disease and positive thyroid-stimulating immunoglobulin values were available for analysis. Of the 35 live births, there were six cases of neonatal thyrotoxicosis (17.1%). A maternal thyroid-stimulating immunoglobulin value at least 5 index units predicted neonatal thyrotoxicosis with a sensitivity of 100%, specificity of 76.0%, positive predictive value of 40.0%, and negative predictive value of 100%. CONCLUSION: Pregnancies complicated by high values of maternal thyroid-stimulating immunoglobulin appear to be at risk of developing neonatal thyrotoxicosis.