Pelvic effusion of 18mm is not serious, women with pelvic effusion is physiological effusion, may also be pathological effusion, the reasons are as follows: First, physiological effusion, more common in late ovulation, related to the ovarian egg discharge, after the menstruation clean review pelvic effusion will be reduced, a small amount of fluid can play a role in lubricating the pelvic organs. Secondly, pathological pelvic effusion may cause pain in the lower abdomen, fever, and lumbago, which will be relieved by pelvic physiotherapy and cefradine for anti-inflammatory treatment. Under normal circumstances, if the diameter of pelvic fluid in women is less than 3cm, and there is no lower abdominal pain, lumbago and fever, it can be temporarily observed because of its own absorption ability.