hi The universal screening of asymptomatic pregnant women for thyroid dysfunction during the first trimester of pregnancy is controversial. We suggest a targeted approach rather than universal screening ). We favor screening pregnant women if they are from an area of moderate to severe iodine insufficiency; have symptoms of hypothyroidism; have a family or personal history of thyroid disease; or have a personal history of thyroid peroxidase antibodies, type 1 diabetes, head and neck radiation, recurrent miscarriage, morbid obesity, or infertility. In women who meet the screening criteria, we measure serum TSH during the first trimester as the screening test for hypothyroidism. If the serum TSH is normal, no further testing is performed. If the TSH is 2.5 mU/L, free T4 should be measured to determine the degree of hypothyroidism. In pregnant women with subclinical hypothyroidism (TSH 2.5 mU/L with a normal free T4), we also measure thyroid peroxidase antibodies. All pregnant women with newly-diagnosed overt hypothyroidism (TSH above trimester-specific normal reference range [2.5 mU/L for first, and 3.0 mU/L for second and third trimesters] with low free T4) should be treated with thyroid hormone (thyroxine, T4). In addition, we suggest initiating T4 replacement in pregnant women with subclinical hypothyroidism (TSH above trimester-specific normal reference range with normal free T4) Women with preexisting hypothyroidism who are planning to become pregnant should optimize their thyroid hormone dose preconception. The goal preconception serum TSH level is take care