CA125 is mainly used to assist in the diagnosis of gynecological cancers and gastrointestinal cancers. Elevated CA125 levels are considered to be caused by the following reasons: 1. Patients may be suffering from ovarian cancer, which may lead to a significant increase in CA125 levels in the serum of patients. If the patient is pregnant, the CA125 level may also be elevated in the first trimester of pregnancy. 3. If the patient has pelvic tuberculosis, the CA125 level may also be elevated, even up to ten times.