What causes menstruation twice a month?

A month to two menstruation, if the second menstrual volume is relatively small, but also in the middle of menstruation, then consider ovulation bleeding. If the two menstrual volume is similar, generally considered menstrual disorders caused by some due to excessive pressure or environmental changes, excessive weight loss, this may also cause this menstrual abnormality. There is to consider whether there is abnormal uterine bleeding, more common reasons are cervical cancer, cervical polyps, endometrial polyps, and submucosal myoma, endometriosis, pelvic inflammatory disease, etc. If a month to two menstruation, first go to the hospital gynecology to do a check, there are B ultrasound, if necessary, check a female hormone six, according to the results and symptomatic treatment.