An endometrial lining of 8.8 millimeters on the 3rd day of menstruation is not normal. The main reason why women have menstruation is caused by the shedding of the uterine lining, so during menstruation the lining of the uterus is relatively thin, which is about 2~3 millimeters. The duration of each menstrual period in women is 2-8 days, with an average of about 5 days. The third day of menstruation should still be during menstruation, when the endometrium is 8.8 mm, is not a normal phenomenon, to consider whether there is an endocrine disorder, may also be caused by endometrial lesions and other factors. If this symptom occurs in adolescent girls, it may be dysfunctional uterine bleeding, which is caused by the ovaries not being able to ovulate regularly, you can take progesterone or dextroprogesterone under the guidance of the doctor to promote the shedding of the uterine lining. Women who have a history of sexual intercourse with this kind of endometrial thickening, it is best to diagnostic scraping for pathologic examination, because to rule out endometrial pathology.