Clinical recommendation	Evidence rating	References
The optimal method to assess serum FT4 during pregnancy uses direct measurement techniques. Serum TSH is a more accurate indicator of maternal thyroid status than alternative FT4 assay methods.	C	3, 6
Targeted screening for thyroid disease should be performed in pregnant women at high risk, including those with a history of thyroid disease, type 1 diabetes mellitus, or other autoimmune disease; current or past use of thyroid therapy; or a family history of autoimmune thyroid disease.	C	2, 3
Hypothyroidism during pregnancy should be treated with levothyroxine, with a serum TSH goal of less than 2.5 mIU per L.	A	1–3
Serum TSH should be measured in pregnant women who are being treated for hypothyroidism at four to six weeks' gestation, then every four to six weeks until 20 weeks' gestation and on a stable medication dosage, then again at 24 to 28 weeks' and 32 to 34 weeks' gestation.	C	2, 3
Propylthiouracil is the preferred agent for the treatment of hyperthyroidism during the first trimester of pregnancy and in women with methimazole (Tapazole) allergy and hyperthyroidism. Consideration should be given to switching to methimazole after the first trimester, and the dosage should be adjusted to maintain a serum FT4 level in the upper one-third of the normal range.	C	3
In pregnant women who are being treated for hyperthyroidism, serum TSH and FT4 should be measured every two weeks until the patient is on a stable medication dosage.	C	2, 3