Causes of low and delayed menstrual flow: 1. Low and delayed menstrual flow may be pregnancy. If a woman is pregnant, it is possible to have delayed menstruation and have low menstrual flow. In fact, it is caused by pregnancy with pre-eclampsia or ectopic pregnancy, further examination of blood HCG value, progesterone and gynecological ultrasound is needed to decide how to deal with it next according to the examination. 2. It is also seen in menstrual disorders, for which further examination of sex hormone six and gynecological ultrasound is needed, according to the examination results, progesterone withdrawal bleeding treatment can be considered, such as Didrogestrel tablets, Imazin, Angioten Most of them will increase the amount of menstruation after the above treatment.