The normal range of TSH during pregnancy varies from week to week of pregnancy. TSH refers to thyroid-stimulating hormone, and TSH ranges from 0.1 to 2.5 mlU/L in early pregnancy, 0.2 to 3.0 mlU/L in mid-pregnancy, and 0.3 to 3.0 mlU/L in late pregnancy. After a woman becomes pregnant, the demand for thyroid hormone by the mother and the fetus begins to increase from the 6th week until an equilibrium can be reached at the 20th week of pregnancy. If TSH decreases and free T₄ or total T₄ increases during pregnancy, it is considered to be combined hyperthyroidism during pregnancy, and if TSH is higher than the upper limit of the reference value during pregnancy, it is considered to be hypothyroidism during pregnancy, both of which will affect the pregnant woman and the fetus, and increase the risk of miscarriage, preterm labor, low-birthweight babies, and stillbirths. Women should follow the doctor’s instructions for regular checkups during pregnancy, and if the TSH value is not normal, talk to the doctor as soon as possible and deal with the situation accordingly.