Hello, and I hope I can help you today. Overactive thyroid is actually normal in some women during the first trimester of pregnancy, because the pregnancy hormone stimulates the thyroid and its levels are highest in the first trimester. It is not dangerous unless your levels are very high and you have symptoms (like a racing pulse or heart palpitations). Severe overactive thyroid can lead to a condition called thyroid storm, which can cause heart failure and other complications; but again, this danger is only to the mother. Your OB provider should refer you to see a specialist if your levels are so high that you may need medication. When the baby is born, it is important for the baby s pediatrician to know about your thyroid history, as sometimes the baby s hormone level can be too low after birth because it has received so much thyroid hormone from you while it was inside. I want to reassure you that treating your thyroid hormone level really depends on how high it is, and many patients do not even need medication. Discussion with your prenatal care provider should help in determining if you need medication. You may need to see an endocrinologist who can prescribe medication to lower your levels of thyroid hormone if they are at a dangerous level. I hope i was able to adequately answer your question today and that my advice was reassuring to you. Best wishes, and good luck with the rest of the pregnancy, Dr. Brown