The thickness of the endometrium changes with the monthly cycle, and the thickness of the endometrium varies during different periods of menstruation. The thickness of the endometrium changes cyclically. The changes of the endometrium in each period are as follows: 1. Proliferative phase: The proliferative phase of the endometrium generally occurs on days 5 to 14 of the menstrual cycle, which corresponds to the follicular development and maturation stage. The endometrium gradually thickens to about 3-5mm. 2. Secretory phase: The endometrium is thickened and appears spongy in shape. At this time, the thickness of the endometrium is about 5-10mm. 3.Menstrual period: Menstruation is an important physiological period for women, when both estrogen and progesterone drop, and the endometrium gradually regains its calmness and begins to grow and adjust, and the thickness of the endometrium at this time can reach 8-10mm. Generally, the endometrium after pregnancy will rapidly proliferate to provide conditions for embryonic growth and development, and a thin endometrium is not protective for The endometrial lining is too thin to protect the fetus, and it is generally optimal to have an endometrial thickness of more than 1 cm for pregnancy. The thickness of the endometrium will continue to increase after pregnancy, and it is only normal to exceed 1 cm. If the endometrium is too thin or too thick, you need to go to the hospital for examination and use medication under the guidance of your doctor.