Aunt only a little, dark, is a decrease in menstrual flow. There are more reasons for reduced menstrual flow. The most common one is endocrine disorder, which means that there is no ovulation. Since there is no follicle growth, the estrogen level is lower and the endometrium becomes thinner without the influence of estrogen, so that the menstrual flow is less when you have your period. The small amount of menstruation encounters acidic discharge from the vagina, so it turns dark brown. At this time, you must go to the hospital to check the sex hormone six and thyroid hormone to see if the endocrine secretion is normal. In case of reduced menstrual flow after abortion or curettage, it is caused by endometrial damage or uterine adhesions, which requires hysteroscopy.