Subclinical hypothyroidism and/or the presence of thyroid peroxidase antibodies (TPOAb) may be associated with subfertility, infertility, spontaneous abortion, placental abruption, preterm delivery, gestational hypertension, preeclampsia, postpartum thyroid dysfunction, depression (including postpartum depression), and impaired cognitive and psychomotor child development. In November 2002, the American Association of Clinical Endocrinologists (AACE) released new guidelines for clinical practice for the diagnosis and treatment of hyperthyroidism and hypothyroidism, which includes a new thyroid-stimulating hormone (TSH) reference range of 0.3 to 3.0 mIU/L. Recently, the AACE recommended screening all women considering conception and/or all gravid women in the first trimester for thyroid dysfunction. However, the American College of Obstetricians and Gynecologists (ACOG) and the United States Preventive Services Task Force (USPSTF) have not endorsed these recommendations. This article reviews the evidence regarding screening women during pregnancy for subclinical hypothyroidism and/or the presence of thyroid peroxidase antibodies.