The thickness of endometrium 0.8cm should not be close to menstruation, the thickness of endometrium normally changes with the menstrual cycle, the thickness of endometrium should reach 1.0cm before menstruation, but it does not mean that the thickness of endometrium can determine whether menstruation is coming or not, the thickness of endometrium may be between 1.0-2.0cm when menstruation comes, depending on individual differences. The onset of menstruation can be predicted by the day of ovulation, which is usually 14 days after ovulation, and if there is no pregnancy, you should have your period. It is clinically difficult to determine the onset of menstruation by the thickness of the endometrium because it is different for each person.