The endometrium is a layer of mucosal tissue in the inner wall of the uterus that changes with the sexual cycle (menstrual cycle) in response to hormonal changes in the body, meaning that the endometrium responds to both estrogen and progesterone. The endometrium can thicken or thin during different phases of the menstrual cycle. The endometrial lining is normally 7mm thick during the follicular phase and is not too thin or too thick. If you are not sure, you can go to the obstetrics and gynecology department for a hormone level check to see the secretion of the body’s hormone levels, if the secretion of the hormone levels are within the normal range, then there is no need to worry and stress. In addition, the thickness of the endometrium will change as the female body is in different periods. When the endometrium is completely shed after menstruation, it will become thinner accordingly. If a normal woman has a vaginal ultrasound after menstruation, it is normal if the thickness of the endometrium is about 4mm; around the time of ovulation the thickness of the endometrium can reach 8-10mm; and when the menstruation is about to come, if there is no pregnancy, sometimes the thickness of the endometrium may reach about 12mm. In short, the normal thickness of the endometrium in women can generally be around 4-10mm. In the follicular phase, if the endometrium is 7mm thick, it is normal and does not belong to too thin or too thick.