The most common cause of hypothyroidism, Hashimoto’s Thyroiditis, occurs in women of childbearing age. Therefore, the treatment of hypothyroidism while preparing for conception and pregnancy is not a minority of mothers-to-be, so that a weak sick horse and then wearing heavy armor to run to the battlefield, the results can be imagined. 2, a variety of reasons for the new onset of hypothyroidism during pregnancy This is also understandable, due to the existence of certain problems in the thyroid gland itself, although it can barely perform its daily work, not to show any abnormality, but can not withstand the high intensity of the load of the state of pregnancy. It is just like the Sino-Japanese War before the North Atlantic naval division, usually flaunted the first in East Asia, in fact, internal and external problems and crises, to the face of a powerful opponent in wartime, quickly collapsed and crumbled. Regardless of the situation, it needs to be clear: hypothyroidism in pregnancy must be corrected, otherwise it is likely to lead to the occurrence of many adverse pregnancy events, including miscarriage, preterm labor, pre-eclampsia, gestational hypertension, postpartum hemorrhage, low birth weight, stillbirth, and fetal mental and psychological developmental damage, and so on. First of all, the prevention of hypothyroidism in pregnancy: 1, for the treatment of hypothyroidism, and plan to get pregnant, the recommendations are: (1) through the treatment of serum TSH control to <2.5miu / l level before pregnancy, the more ideal goal is to let tsh between 0.1-1.5mIU / L; (2) once pregnant, the drug dose in the original basis of an increase of 25% -30%, the most (2) Once pregnant, the dose should be increased by 25%-30% from the original dose, the easiest way is to take the dose for two extra days per week (29% increase), and then adjust it according to the target value. 2, for no history of hypothyroidism, in other words, for all healthy pregnant women, although due to the limitations of the national situation, China has not yet pregnant women to carry out thyroid function screening, but still recommended: (1) recommended that pregnant women with the conditions of early pregnancy screening for thyroid disease, the screening content includes: serum TSH, FT4, TPOAb; (2) screening time to choose in the pregnancy before the eighth week, preferably in the pre-pregnancy. In the special state of "pregnancy", many expectant mothers are afraid of the words "disease" and "medication". In fact, as long as the timely diagnosis, "hypothyroidism in pregnancy" is not at all terrible. Its treatment can even be summarized in three words: effective, safe and economical. As long as you grasp the following principles, there is no worry about the smooth passage: 1, "levothyroxine (LT4)" is currently the only correct treatment of hypothyroidism in pregnancy medication, if someone is still using the thyroid tablets, LT3, or LT4/LT3 combined preparations, should be changed, change the doctor; 2, serum TSH is the most important therapeutic assessment indexes The target value varies in each period of pregnancy, specifically: 0.1-2.5 mIU/L in early pregnancy (0-12 weeks), 0.2-3.0 mIU/L in mid-pregnancy (13-27 weeks), and 0.3-3.0 mIU/L in late pregnancy (28-40 weeks); 3. At the end of the pregnancy, it is important to adjust the LT4 dosage back to the pre-pregnancy level and it is recommended that the TSH be rechecked at 6 weeks post-partum levels for further dose adjustment. The actual clinical situation is much more complex than the above understatement. For example, between "normal" and "hypothyroidism," there is the "subclinical hypothyroidism" state. Subclinical hypothyroidism is a condition in which a pregnant woman's serum TSH level is higher than the upper limit of normal for pregnancy, while her FT4 level remains normal. This is roughly the state in which the thyroid has worked overtime to complete its assigned task, but is tired and unloved. More and more studies have shown that this state also increases the risk of pregnancy, but treatment or not needs to refer to another important indicator: thyroid peroxidase antibodies (TPOAb). 1. If TPOAb is negative, treatment is controversial and non-committal due to insufficient evidence-based evidence; 2. If TPOAb is positive, LT4 treatment is recommended, with the same goals of treatment as before. In addition, as long as TPOAb is positive, even if TSH and FT4 are normal, it is necessary to review the thyroid function regularly, this is because it reflects that the thyroid gland is suffering from autoimmune damage, and it is only a matter of time before it goes from compensated to decompensated.