Objective: To identify risk factors for disorders of fetal growth and thyroid function in the presence of maternal Graves disease.
Methods: Two hundred thirty pregnancies in gravidas with Graves disease were analyzed. Maternal thyroid status was evaluated by serum free thyroxine (T4) or free T4 index, TSH, and TSH-receptor antibody; personal history of thyrotoxicosis and total dose of antithyroid drugs during pregnancy were also noted. Neonatal thyroid function was assessed at birth and on the fifth day after birth.
Results: Fifteen neonates (6.5%) were small for gestational age (SGA), and this occurrence was significantly associated with thyrotoxicosis lasting for 30 weeks or more of pregnancy, TSH-receptor antibody level of 30% or more at delivery, history of Graves disease of 10 years or longer, and onset of Graves disease before 20 years of age. However, no significant correlation was found between maternal thyroid hormone level and SGA neonates. Thyroid dysfunction developed in 38 infants (16.5%), of whom only four were SGA; development of this dysfunction was significantly related to the mother's total dose of antithyroid drugs, duration of thyrotoxicosis in pregnancy, and/or TSH-receptor antibody level at delivery.
Conclusions: Duration of maternal Graves disease or thyrotoxicosis, either mild chemical or overt, in pregnancy is significantly associated with SGA neonates. Neonatal thyroid dysfunction is associated with the maternal thyroid condition, especially the serum TSH-receptor antibody level.