Most women do not have a lot of menstrual blood on the first day of menstruation, and the second day is the largest day of menstruation. Normally, there is no blood clot in the menstrual blood, and the menstrual blood is non-clotting, and it is normal for some women to have small blood clots. When the blood clots are bigger, it is a clinical abnormality, which may be caused by the following reasons: firstly, sub-membranous fibroids, which will not only cause blood clots, but also increase the amount of menstrual flow and shorten the menstrual cycle; secondly, inflammation of the uterine endometrium, which will also lead to clots; thirdly, abnormal position of the uterus, such as backward bending, backward tilting, or anterior and anterior tilting, which will cause menstrual blood not to flow smoothly and clots will be formed. Thirdly, abnormal position of the uterus, backward and backward tilting or forward and forward tilting of the uterus, which makes the menstrual blood not flow smoothly, may form clots. Clinically, if you find large clots in menstrual blood, you must do the appropriate examination, and according to the results, then make the appropriate treatment.