Whether pelvic effusion of 3 cm is serious or not needs to depend on what type of pelvic effusion it is, if it is physiological, it is usually not serious; if it is pathologic, it is considered that it may be more serious. 1. Physiologic pelvic fluid: Generally speaking, most of the physiologic pelvic fluid is less than 1 cm, but there are also more than this range, but without any symptoms. Usually, it can be observed and then checked to see if it is absorbed. 2. Pathologic pelvic effusion: Most of them are caused by pelvic inflammation, and may be accompanied by abdominal pain or abnormal secretions. If you find pelvic effusion of 3 cm, it is recommended that you consult a doctor in time, complete the relevant examinations, and identify the cause of the targeted treatment under the guidance of a professional doctor, so as to avoid delaying the condition.