Fluid in the uterine cavity in early pregnancy may be caused by the fertilization of the egg, or it may be caused by the occurrence of preeclampsia, or endometrial polyps, uterine fibroids and other diseases. 1. Fertilized egg implantation: usually considered to be due to the implantation of the fertilized egg, a small portion of the endometrium was damaged, resulting in a small amount of bleeding, the presence of uterine fluid detected in early pregnancy, is a physiological uterine fluid. 2. Pre-eclampsia: It is mostly considered that it may be due to the presence of chromosomal abnormalities of the embryo, serious infections, luteal insufficiency, sperm deformities, excessive exposure to radioactivity, etc., which in turn affects the development of the embryo, and if the amount of bleeding is too much, then it will be manifested as the uterine cavity fluid in the early stage of pregnancy. 3. Endometrial polyps: the etiology of this disease is not yet clear, and may be caused by inflammatory stimulation, estrogen levels are too high. Generally, small polyps are asymptomatic, but if the polyps are large, abnormal uterine bleeding will occur, so the presence of fluid in the uterus can be detected by examination in early pregnancy. 4. Uterine fibroids: Studies have shown that this disease may be related to heredity, sex hormone levels and other reasons. Because the fibroid protruding into the uterus will make the uterine cavity deformed, resulting in insufficient blood supply to the endometrium, so to a certain extent, it will affect the normal pregnancy, and then there is fluid in the uterine cavity in early pregnancy. There are many causes of fluid in the uterine cavity in early pregnancy, so it is necessary to go to the hospital for consultation to clarify the specific causes and follow the doctor’s instructions for treatment.