How can Graves' disease affect pregnancy?

After treatment with surgery or radioactive iodine, thyroid-stimulating antibodies can still be present in blood even though thyroid levels are normal. In a pregnant woman who received either of these treatments, the antibodies she produces may travel across the placenta to the baby's bloodstream and stimulate the fetal thyroid. A pregnant woman who has been treated with surgery or radioactive iodine should inform her doctor so that her baby can be monitored for thyroid-related problems later in the pregnancy.

This answer is based upon information from the National Institute of Diabetes and Digestive and Kidney Disease.