Menstrual stomach pain is collectively called dysmenorrhea, with dysmenorrhea and black blood clots, there may be the following reasons: 1, inflammation of the pelvic cavity leads to stomach pain when menstruation, pelvic inflammation when the pelvic cavity was in a state of congestion, menstruation makes the original congestion of the pelvic cavity aggravated, there is stomach pain, and with inflammation, the color of menstrual blood will become darker and blood clots will appear. 2, abnormal development of the uterus caused by, if the uterus abnormalities, such as having a longitudinal uterus, saddle-shaped uterus, or unicornuate uterus, can also cause menstrual pain and black blood clots in menstrual blood. It is recommended to do gynecological examination to know whether there is inflammation and to do ultrasound examination to exclude uterine abnormalities.