The guidelines were developed by several international expert groups: 1; Diagnosis of subclinical or clinical hypothyroidism based on serum TSH levels in early pregnancy >2-5mIU/L, mid pregnancy 0-2-3-0mIU/L, late pregnancy 0-3-3-0mIU/L. For the first time, it was clearly stated that the diagnosis of subclinical or clinical hypothyroidism was based on serum TSH levels in early pregnancy >2-5mIU/L, mid and late pregnancy >3 The diagnosis of subclinical or clinical hypothyroidism is confirmed by serum TSH levels >2-5mIU/L in early pregnancy and >3-0mIU/L in mid- to late-pregnancy, combined with serum FT4 levels. 2; Treatment of subclinical hypothyroidism with positive autoantibodies to the thyroid gland must be treated with levothyroxine zLDT4{, the goal is to have serum TSH levels within the normal range in the third trimester, and LDT4 must be used as the first recommended therapeutic drug. for the treatment of pure subclinical hypothyroidism, serum TSH >10 mIU/L is treated as clinical hypothyroidism regardless of FT4 levels. 3; For simple low T4emia, treatment is not recommended at present. For simple autoantibody positive patients, follow-up is recommended once in 4 weeks and once in the middle and late pregnancy. 4; The daily iodine intake of pregnant women should not exceed 500 to 1100ug.