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It is most important for women with Graves' disease (GD) to be euthyroid before conceiving. Ideally, women should plan to conceive only when their Graves' disease is under control because the rate of miscarriage and birth defects is significant in untreated women. Women with Graves' disease who conceive or women who develop Graves' disease during pregnancy must be monitored closely by their physician throughout the pregnancy.

Many women choose to undergo RAI before trying to conceive in order to achieve euthyroidism. For women who are not euthyroid or who develop Graves' disease during pregnancy, low doses of antithyroid drugs can be given. Historically, PTU was the drug of choice but there is increasing evidence that MMI may also be safe for the fetus. Antithyroid drugs can cross the placenta and may cause fetal goiter or hypothyroidism, however, the risk is considered to be low. Many doctors feel that it is safe for a woman to breast feed while taking antithyroid drugs.

Under some circumstances, a second trimester thyroidectomy may be considered. Sometimes, spontaneous remission of Graves' disease occurs in the third trimester of pregnancy. Relapse of Graves' disease may occur in the post-partum period.

Approximately 1-5% of infants born to women with Graves' disease during pregnancy are born with hyperthyroidism due to the passage of thyroid stimulating antibodies across the placenta. Neonatal hyperthyroidism is determined by measuring maternal serum levels of thyrotropin-receptor antibodies at the beginning of the third trimester. If the fetus shows evidence of hyperthyroidism, it can lead to:

• Reduced intrauterine growth
• Intellectual retardation
• Tachycardia (rapid heart beat)
• Early mortality

In newborns with hyperthyroidism, there may be evidence of tachycardia, irritability and weakness.