Pregnant women are at an increased risk of developing thyroid dysfunction as compared to the general population. Any woman with a prior history of a thyroid problem, a family history of thyroid disease or symptoms of thyroid dysfunction should be tested for thyroid dysfunction as soon as she knows she is pregnant. TH (T4) is absolutely safe to take during pregnancy and is essential for the health of the fetus if you are diagnosed with hypothyroidism. If you are diagnosed with hyperthyroidism, antithyroid drugs may be used. If a woman is allergic to these drugs, surgery may also be considered at certain times during the pregnancy (the second trimester). Radioactive iodine is not an option during pregnancy because it will pass into the fetus and damage its thyroid gland.