Hypothyroidism in pregnant women is divided into the following two cases: First, if you already suffered from hypothyroidism before pregnancy, you should continue to take oral levothyroxine tablets for treatment during pregnancy and adjust the dosage of medication according to the changes of thyroid hormones during the pregnancy week, both to control thyroid hormone normally and to control thyroid stimulating hormone below 2.5mU/L in early pregnancy and below 3.0mU/L in middle and late pregnancy. If the thyroid gland function is normal before pregnancy and the thyroid hormone level is normal during pregnancy, but the thyroid stimulating hormone level is slightly higher, then if the thyroid autoantibodies are positive and the thyroid stimulating hormone level in the blood is higher than 2.5mU/L, levothyroxine tablets should be given; if the autoantibodies are negative, levothyroxine tablets should be given only when the thyroid stimulating hormone in the blood is generally higher than 4.0mU/L. If the autoantibodies are negative, levothyroxine tablets should be given only when the blood thyroid hormone is above 4.0 mU/L. The control criteria are the same as before. This type of hypothyroidism during pregnancy does not usually require long-term treatment.