A dark intrauterine fluid area is a problem of fluid or blood accumulation in the uterine cavity detected by ultrasound. Some women’s uterus is too tight at the endocervix or posterior uterus, which may cause difficulty in menstrual blood discharge and stagnation in the uterine cavity, and the problem of liquid dark area indicated by ultrasound examination can be treated without treatment as a physiological problem, just pay attention to keep warm during menstruation. Inflammation of the endometrium of the uterus stimulates the uterine cavity and produces fluid in the uterine cavity. Infection with bacteria can cause pus in the uterine cavity and high fever, which can be treated with systemic antibiotics. In the early stages of pregnancy, bleeding caused by the destruction of the endometrium due to embryo implantation may also cause a slight accumulation of fluid in the uterus. If the fetal appendages are not removed cleanly after the abortion, a dark area of fluid in the uterine cavity can also be seen.