There is fluid during pregnancy, which may be manifested as fluid in the uterine cavity or pelvic cavity. causes of fluid during pregnancy, mainly include fluid that occurs in the uterine cavity, this has the following causes: 1. it may be due to insufficient progesterone level in the body during pregnancy, which affects the normal development of the gestational sac, resulting in a small amount of bleeding around the gestational sac, which is not discharged in time causing a small amount of fluid. 2. chronic endometritis. The chronic endometritis is suffered before pregnancy itself, and the inflammatory secretion exuding cannot be discharged and accumulates in the uterine cavity. In addition, it also includes pelvic effusion, which is introduced as follows: 1, pregnant women suffer from chronic pelvic inflammatory disease before pregnancy, causing a small amount of pelvic effusion, but it is not detected in time before pregnancy. 2, after pregnancy, due to the accelerated blood circulation in the pelvic cavity, a small amount of tissue fluid exudes and accumulates in the pelvic cavity causing effusion.