When the menstrual period has not yet come, the lumbar pain is caused by many reasons, such as recent heavy physical labor, standing time is more often, sitting and standing time is also longer, when there is pelvic inflammatory disease, it may also cause lumbar pain, or before the menstrual period, due to the pelvic vasodilation, stimulation of the lumbosacral blood vessels may also cause lumbar pain, which belongs to premenstrual This is PMS and it is recommended to follow up and observe. The normal time of menstruation is 28-30 days, and occasionally there is a delay, as long as there is no pregnancy, it will not cause health problems.