The normal endometrial thickness in women varies from 5-10 mm during the different cycles of menstruation. The endometrial thickness is about 9-10 mm in the proliferative phase and 5-6 mm in the secretory phase. The endometrial thickness reaches 8-10 mm during menstruation. The thickness of the endometrium varies with the cyclic changes of the ovaries. Starting on day 5 of the menstrual cycle, the endometrium is in a proliferative phase and the lining thickens continuously, up to 3-4 mm thick by day 14 of menstruation. In the second half of the menstrual cycle, the endometrium is in the secretory phase, but continues to thicken. By the time of menstruation, the endometrium can finally reach 10 mm. Therefore, the normal thickness of a woman’s endometrium is 8-12 mm, with a minimum of not less than 6 mm. Generally speaking after a recent pregnancy, the endometrial thickness needs to be around 10 mm. According to experts, the minimum endometrial thickness that is conducive to conception is about 8 mm and the endometrial phase for conception is preferably in the luteal phase.