A small amount of fluid in the uterine cavity in the third trimester of pregnancy is usually not dangerous, but a large amount may be dangerous. If the amount of fluid in the uterine cavity in the third trimester of pregnancy is small, the pregnant woman does not have any discomfort symptoms such as lower abdominal distension and pain, and there is no redness of the situation, it is usually fine. Blood tests for progesterone and human chorionic gonadotropin can be done at the hospital in time. It is recommended that you stay in bed more often in order to promote self-absorption of the fluid, and that you have regular checkups. If the amount of fluid in the uterine cavity is relatively large or there are clinical symptoms such as vaginal bleeding, it may cause the fetus to have infections, chorioamnionitis and other problems, which will have a greater impact on the development of the fetus, and this situation is more dangerous. Uterine fluid in the third trimester of pregnancy needs to be treated under the guidance of the doctor, and at the same time need to pay attention to bed rest, forbidding sexual life, strengthen the maternity examination and so on.