Gestation is the physiological period after conception and before delivery, a physiological term also known as the pregnancy period. From the time of fertilization of a mature egg to the delivery of the fetus, it is usually about 266 days. For calculation purposes, pregnancy is usually counted from the first day of the last menstrual period, and a full-term pregnancy is about 280 days (40 weeks). During pregnancy, the maternal metabolism, digestive system, respiratory system, vascular system, nervous system, endocrine system, reproductive system, bone and joint ligaments and breasts all undergo corresponding changes. 1. 3rd trimester: specific TSH reference value. That is, 0.1 – 2.5 mlU/L in early pregnancy, 0.2 – 3.0 mIU/L in mid pregnancy, 0.3 – 3.0 mlU/L in late pregnancy. 2, 3 stages of pregnancy, that is, early pregnancy (l-12 weeks of gestation), mid pregnancy (13-27 weeks of gestation), late pregnancy (28-40 weeks of gestation) The diagnostic criteria for clinical hypothyroidism in pregnancy: TSH > the upper limit of the reference value in pregnancy, and FT4 < the reference value in pregnancy. and FT4 < the lower limit of the reference value during pregnancy. In women with TSH >10 mIU/L in early pregnancy, clinical hypothyroidism can be diagnosed with or without FT4 reduction. The goals of serum TSH treatment for clinical hypothyroidism in pregnancy are: 0.1-2.5 mlU/L in early pregnancy, 0.2-3.0 mlU/L in mid pregnancy, and 0.3-3.O mlU/L in late pregnancy. Under what conditions can a woman with clinical hypothyroidism become pregnant? The specific treatment goals are: serum TSH 0.1 to 2.5 mlU/L, and more ideally, TSH 0.1 to 1.5 mlU/L. Frequency of monitoring clinical hypothyroidism in pregnancy After pregnancy, thyroid function, including serum TSH, should be monitored every 4 weeks during the first half of pregnancy in patients with clinical hypothyroidism. According to the control goal. Adjust the L-T4 dose and test thyroid function every 4 weeks. The diagnostic criteria for subclinical hypothyroidism in pregnancy and whether to treat it are: serum TSH > the upper limit of the pregnancy-specific reference value, and serum FT4 within the reference value. L-T4 therapy is recommended for pregnant women with TPOAb-positive subclinical hypothyroidism; for pregnant women with TPOAb-negative subclinical hypothyroidism, L-T4 therapy is neither opposed nor recommended.