Pregnant women with hypothyroidism are divided into the following two cases: First, if you have already suffered from hypothyroidism before pregnancy, continue to take oral levothyroxine tablets for treatment during pregnancy and adjust the dosage of the medication according to the change of thyroid hormone during the pregnancy week, not only the thyroid hormone control is normal, but also the thyroid stimulating hormone is controlled to be less than 2.5 mU/L in early pregnancy, and less than 3.0 mU/L in the middle pregnancy and late pregnancy. If thyroid autoantibodies are positive and thyrotropin level in blood is higher than 2.5mU/L, levothyroxine tablets should be given to control the thyrotropin level; if autoantibodies are negative and thyrotropin is generally higher than 4.0mU/L, levothyroxine tablets should be given to control the thyrotropin level and control the thyrotropin level. If the autoantibody is negative, levothyroxine tablets will be given only when the blood thyrotropin is above 4.0mU/L. The standard of control is the same as the previous one.