Menstruation does not usually occur after pregnancy, but if there is a preeclampsia, etc. there may be a small amount of vaginal bleeding, which is mistaken for menstruation. Low menstrual flow may be related to polycystic ovary syndrome, endocrine disorders, gynecological inflammation and other reasons. 1. Pre-eclampsia: small amount of vaginal bleeding may occur in early pregnancy when the fertilized egg is unstable, it is recommended to take bed rest, avoid sexual intercourse, and take oral progesterone, dydrogesterone and other medications to protect the fetus. 2. Polycystic Ovary Syndrome (PCOS): It can be manifested as menstrual disorders, such as scanty menstruation, amenorrhea and other symptoms, as well as hirsuteness, acne, hair loss and other hyperandrogenic symptoms, which can be clearly diagnosed through the examination of sex hormone six and ultrasonography. 3. Endocrine disorders: If a woman has recently worked under great pressure, lived an irregular life, or changed her living environment, it will cause endocrine disorders, leading to abnormal menstruation and low menstrual flow. 4. Gynecological inflammation: If a woman has had an abortion, it is easy to cause infection in the uterine cavity, resulting in adhesions in the uterine cavity, and the menstrual blood is not easy to be discharged, which will make the menstrual flow decrease. It is important to note that there are many causes of low menstrual flow, it is recommended to consult a doctor in time to clarify the cause of the disease and actively treat it.