Not having a period but having blood belongs to intermenstrual bleeding, which may be caused by ovulation, or uterine fibroids, cervicitis, preeclampsia, cervical cancer and other factors. 1. Ovulation bleeding: Ovulation bleeding is mainly caused by a brief drop in hormone levels in the body, resulting in a loss of hormonal support for the endometrium. This is mostly a normal phenomenon, and the bleeding time is usually short and the amount of blood is relatively small. 2. Uterine fibroids: As the growth of the tumor will protrude into the uterine cavity, the area of the endometrium will increase, which will easily cause bleeding between periods. Patients may also have symptoms such as increased menstrual flow, dysmenorrhea, abnormal vaginal discharge, and lower abdominal distension. 3. Cervicitis: this disease is mainly due to pathogen infection, is a common gynecological disease will lead to local congestion, edema, easy to appear intermenstrual bleeding, mainly contact bleeding, especially after sex. 4. Pre-eclampsia: If the patient is already pregnant, she usually does not have menstruation. Influenced by embryonic development, maternal factors, chromosomal abnormality of sperm, environment and so on, it may cause premenstrual abortion and bleeding between periods, and the patient may also be accompanied by lower abdominal pain or low back pain. 5. Cervical cancer: Cancer cells will invade blood vessels, resulting in fragile blood vessels that are easy to rupture and bleed, and bleeding between periods will appear, which is also the most common symptom of cervical cancer. In the early stage, it is mostly intermittent, painless and contact bleeding, while in the late stage, it can be prolonged and repeated vaginal bleeding. Besides, taking contraceptive pills, endometrial polyps, ectopic pregnancy, luteal insufficiency and so on can also lead to intermenstrual bleeding, and patients need to consult doctor for examination and treatment in time.