Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 19-19: Thyroid Disease in Pregnancy + Key Features Download Section PDF Listen +++ ++ Overt hypothyroidism Associated with an increase in complications such as preterm birth, preeclampsia, placental abruption, and impaired neuropsychological development in the offspring The most common etiology is Hashimoto (autoimmune) thyroiditis Subclinical hypothyroidism Defined as an increased TSH and a normal FT4 level American College of Obstetricians and Gynecologists and the American Association of Clinical Endocrinologists recommend against screening for or treating subclinical hypothyroidism Overt hyperthyroidism Associated with spontaneous abortion, preterm birth, preeclampsia, and maternal heart failure if left untreated Thyroid storm, although rare, can be a life-threatening complication Transient autoimmune thyroiditis can occur in the postpartum period and is evident within the first year after delivery + Clinical Findings Download Section PDF Listen +++ ++ Overt hypothyroidism: Symptoms mimic those of normal pregnancy Overt hyperthyroidism Fetal hypothyroidism or hyperthyroidism are uncommon but can occur with maternal Graves disease, which is the most common cause of hyperthyroidism in pregnancy Transient autoimmune thyroiditis The first phase, occurring up to 4 months postpartum, is a hyperthyroid state Over the next few months, there is a transition to a hypothyroid state, which may require treatment with levothyroxine + Diagnosis Download Section PDF Listen +++ ++ Screening with thyroid function tests Indicated for women who have a history of a thyroid disorder or symptoms that suggest thyroid dysfunction No proven benefit for asymptomatic pregnant women and not currently recommended Overt hypothyroidism Elevated serum TSH level Depressed serum FT4 level + Treatment Download Section PDF Listen +++ ++ Overt hypothyroidism Levothyroxine, 75–100 mcg orally daily Thyroid function tests can be repeated at 4–6 weeks and the dose adjusted as necessary with the goal of normalizing the TSH level An increase in the dose of levothyroxine may be required in the second and third trimesters Overt hyperthyroidism Propylthiouracil or methimazole A beta-blocker can be used to manage palpitations or tremors Radioiodine ablation must be avoided because it may destroy the fetal thyroid as well Transient autoimmune thyroiditis: Spontaneous resolution to a euthyroid state within the first year is the expected course; however, some women remain hypothyroid longer