A large belly in women can be caused by a number of factors. On the one hand, prolonged sitting and standing without exercise can cause fat to accumulate in the abdomen, resulting in an enlarged belly. On the other hand, pelvic tumours, such as ovarian cysts and uterine cysts, or disease factors such as urinary retention or ascites, can also cause the patient to have an enlarged abdomen. In this case, the patient needs to seek medical attention and undergo ultrasound and other tests to confirm the diagnosis.