Subclinical hypothyroidism in pregnancy (SCH) increases the risk of adverse pregnancy outcomes, including miscarriage, preterm delivery, low birth weight babies, and placental abruption. In addition, the fetal thyroid gland begins to secrete thyroid hormone (TH) only from the 12th week of gestation, before which the fetal TH is provided exclusively by the mother. Therefore, SCH during pregnancy may affect the growth and development of the offspring. However, the findings are not uniform in domestic and international studies, and there is a lack of evidence from large studies to draw definitive conclusions. At present, there is no uniform diagnostic index for TSH and T4 during pregnancy in China. Domestic guidelines recommend that, to avoid adverse pregnancy outcomes, pregnant women with positive gestational SCH with TPOAb should receive L-T4 therapy, but there is no clear recommendation on whether pregnant women with negative gestational SCH with TPOAb should also undergo L-T4 therapy.