The uterus, which produces menstruation and nurtures the fetus, is a very important reproductive organ for women and is located at the upper end of the female vagina, in the center of the pelvis. Normally, the uterus is slightly curved forward with its anterior wall lying prone on the bladder, which can change depending on the degree of filling of the bladder and rectum. Its structure is plasma layer, muscle layer and mucosal layer from outside to inside, and the uterine wall is divided into three layers: epithelial layer, muscle layer and endometrium from outside to inside. normal size is 5.5-7.5cm longitudinal diameter, 3.0-4.0cm anterior-posterior diameter, 4.5-5.5cm transverse diameter, and 2.5-3cm long cervix. adult female uterus is about 7-8cm long, 4-5cm wide at the bottom, 2-3cm thick, and weighs about 40-50g. It weighs about 40-50g. The normal size range of the uterus can also vary with the menstrual cycle. The normal endometrium is 1.1 cm during ovulation and 0.6-0.7 cm during non-ovulation. in addition, after pregnancy, the uterus changes to accommodate the growth and development of the fetus. Before pregnancy, the uterus weighs 50g and its volume is about 7cm*4.5cm*3.5cm. By the time of full-term pregnancy, the uterus weighs 1000g, which increases 20 times and can accommodate the fetus and amniotic fluid of about 5000ml. After full term, the uterus is 35cm long, 25cm wide and about 22cm thick. In addition, the size of the uterus is related to age and childbirth, for example, the uterus is larger in women who have given birth and smaller in women who have not given birth.