Changes in the uterus during pregnancy, i.e. gestation, include changes in the size of the uterus, changes in uterine blood flow, changes in the endometrium, and changes in the isthmus of the uterus. 1. Changes in the size of the uterus: with the progression of pregnancy and the development of the fetus, the uterine body gradually enlarges and becomes softer, and by the time the pregnancy reaches full term, its volume can increase by 1000 times, reaching 5000ml. 2. Changes in uterine blood flow: In order to meet the needs of fetal-placental circulation during pregnancy, the blood vessels of the uterus dilate and thicken, and the uterine blood flow increases. 3. Changes in the endometrium: after the fertilized egg is deposited, under the action of estrogen, progesterone and other hormones, the endometrium will have enlarged glands and increased glycogen in the glandular epithelium in order to form the metaphase. 4. Changes in the isthmus of the uterus: the isthmus of the uterus becomes soft after pregnancy. After 12 weeks, it gradually stretches, elongates and thins to form the lower uterine segment, which can stretch to 7~10cm after labor and become part of the soft birth canal. If there is any discomfort, it is recommended to consult a doctor in time for treatment.