Low and black menstruation may be pregnant, but it may also be caused by endocrine disorders, surgical operations, uterine diseases, etc. For clear judgment, it is still necessary to check the blood hCG level or gynecological ultrasound: 1. Pregnancy: If a woman usually has a regular menstrual cycle and a normal sex life, and suddenly has a low and black menstrual flow, it is possible that she is pregnant and has a pre-eclampsia. Once pregnancy is diagnosed and a small amount of vaginal bleeding occurs, preterm miscarriage and ectopic pregnancy should be considered, and pelvic ultrasound examination is needed to assist in the diagnosis; 2, endocrine disorders: if it is clear that there is no pregnancy and the menstrual volume is low and black, it may be related to endocrine disorders, and the fluctuation of hormone levels in the body will affect the menstrual cycle, it is recommended to go to the hospital to do sex hormone six, thyroid function, ultrasound examination Clear diagnosis; 3. Surgical operation: If you have recently done uterine operation, such as abortion, diagnostic scraping surgery, or hysteroscopy, there may be damage to the endometrium due to the surgery, which may also lead to reduced menstrual flow and blackness; 4. Uterine diseases: Conditions such as endometrial damage and uterine adhesions can cause a small amount of bleeding, which can be mistaken for a low menstrual flow.