Pelvic fluid accumulation of 20mm is usually due to physiological reasons, which is not a serious situation; it may also be caused by pathological reasons, which need to be taken seriously. 1. Physiological phenomenon: under normal circumstances, because the pelvis is in the lowest position in the abdominal cavity, there is normally a certain amount of fluid, the abdominal organs play a lubricating, preventing adhesions, especially in the ovulation period, premenstrual period, there will be pelvic effusion 20mm, there is no pain in the lower abdomen and other uncomfortable symptoms, belong to the normal, no need to deal with. 2. Pathological reasons: women suffering from pelvic inflammatory diseases, because of the local inflammatory exudate more, pelvic fluid will increase, greater than 30mm, the patient will also be accompanied by lower abdominal pain and discomfort, and more need to be anti-infective treatment. Can also be due to ectopic pregnancy rupture bleeding, caused by pelvic blood, ultrasound shows pelvic effusion, bleeding can be a small amount, can be a large amount of bleeding, serious patients have hemorrhagic shock symptoms, need timely surgery to remove the lesions. When a woman finds pelvic effusion, a small amount of effusion not more than 30mm, it is mostly a normal phenomenon. If the pelvic effusion is greater than 30mm, it is necessary to go to the hospital in time, and the professional doctor will give the relevant examination, and after the diagnosis is made clearly, the targeted treatment will be carried out.