Menstruation is the cyclical shedding and bleeding of the endometrium under the cyclic regulation of estrogen and progesterone secreted by the ovaries. With the changes of estrogen and progesterone during the menstrual cycle, the mucosa of the vaginal mucosa, the cervical mucosa, and the mucosa of the fallopian tubes and other organs of the reproductive tract also undergoes cyclic changes. For example, during the proliferative phase, the vaginal epithelium proliferates under the action of estrogen, the cells of the basal layer gradually evolve into the middle and superficial layers of cells, the vaginal epithelium thickens, and the superficial cells are keratinized, the degree of keratinization is usually most obvious at the time of ovulation, and the keratinized cells are lined with Glycogen. Parasitic vaginal bacilli, the vagina, glycogen decomposition into lactic acid, so that the vagina to maintain an acidic environment, to prevent the propagation of disease-causing bacteria, at this time and then see the vaginal exfoliative cells, the epithelial cells should not be a lot, but in the role of progesterone after ovulation under the action of the epithelial cells shedding, leading to the observation of the epithelial cells will increase in the number of counts. Therefore, the changes in the vaginal shedding cells can be used to understand the level of estrogen in the body and whether there is ovulation or not, and this change is also more obvious in the upper segment. The increase in epithelial cell count is mainly considered to be related to the effect of estrogen and progesterone.