Serum TSH treatment goals for clinical hypothyroidism in pregnancy:0.1~2.5mIU/L in early pregnancy, 0.2~3.0mIU/L in mid-pregnancy, 0.3~3.0mIU/L in late pregnancy Once clinical hypothyroidism is identified, start treatment immediately to achieve the above treatment goals as early as possible. Levothyroxine:50~100ug once daily to start, check TSH every four weeks, increase or decrease 25ug each time according to TSH level to maintain TSH within normal range. Thyroid indexes should be checked every 4 weeks from 1 to 20 weeks of pregnancy, and serum thyroid function indexes should be tested from 26 to 32 weeks.