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26 Table 12. Summary of Recommendations Concerning Management of Graves' Disease Causing Overt Hyperthyroidism in Pregnancy Timing of diagnosis Specific circumstances Recommendation GD diagnosed during pregnancy Diagnosed during first trimester • Begin propylthiouracil a • Measure TRAb at diagnosis and, if elevated, repeat at 18–22 weeks b and again at 30–34 weeks c of gestation • If thyroidectomy is required, it is optimally performed during the second trimester Diagnosed aer first trimester • Begin methimazole. a • Measure TRAb at diagnosis and, if elevated, repeat at 18–22 weeks b and again at 30–34 weeks c of gestation (all depending on week of diagnosis). • If thyroidectomy is required, it is optimally performed during the second trimester. GD diagnosed and treated prior to pregnancy Currently taking methimazole • Switch to propylthiouracil or withdraw ATD therapy as soon as pregnancy is confirmed with early testing. a • Measure TRAb initially and, if elevated, again at 18–22 weeksb and 30–34 weeks c of gestation. In remission aer stopping antithyroid medication Previous treatment with RAI or surgery • Perform thyroid function testing to confirm euthyroidism. TRAb measurement not necessary. Previous treatment with RAI or surgery • Measure TRAb initially during the first trimester and, if elevated, again at 18–22 weeks of gestation. d a See remarks under Recommendations 93, 96 & 97 for discussion regarding switching from one antithyroid drug to the other during pregnancy or withdrawing from therapy. b If a TRAb-positive woman becomes TRAb-negative during pregnancy, this may indicate a need to reduce or stop antithyroid drug therapy to avoid fetal hypothyroidism. See remarks under Recommendations 99 & 103. c If the antithyroid drug treated mother has high TRAb values in late pregnancy this indicates a risk of delayed neonatal hyperthyroidism (see remarks to Recommendations 97 & 104). d If the mother has undergone some type of thyroid ablation (radioactive iodine or surgery) for GD and TRAb is high, evaluate fetus carefully for hyperthyroidism in second half of pregnancy and adjust or begin antithyroid drug therapy accordingly. See remarks to Recommendation 102. Subclinical Hyperthyroidism and Pregnancy

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