In general, the thickness of the endometrium when grows to about 10 mm when menstruation will come, according to this situation, but also to understand the changes in the growth pattern of the endometrium according to the different periods of the menstrual cycle. At the end of the menstrual cycle, the endometrium is thin, around 4-5mm. As the menstrual cycle continues to change, the endometrium changes from the proliferative phase to the secretory phase during ovulation due to the stimulation of estrogen and progesterone, when the thickness of the endometrium is about 8mm. Due to the continuous secretion of progesterone, the endometrium in the proliferative phase gradually becomes more obvious in the secretory phase, when the endometrium in the secretory phase grows to about 10mm before menstruation.