Low back pain after menstruation is usually caused by the mother’s body has not yet recovered, low back muscle strain, calcium deficiency and other reasons. You can pay attention to rest, maintain a correct breastfeeding posture and take postnatal calcium supplements. 1. The body has not yet recovered: After giving birth to a mother with a large weight change, some mothers may carry out high-intensity exercise to restore the figure, but if the body has not yet recovered or the body can not withstand the intensity of the exercise, it may lead to back pain. At this time, the mother should pay attention to rest, avoid doing high-intensity exercise. 2. Low back muscle strain: If the mother in the breastfeeding process posture is not appropriate, also easy to cause low back muscle strain, so the mother in the breastfeeding process to maintain the correct posture. 3. Calcium deficiency: During pregnancy and breastfeeding, a lot of calcium will be provided to the child, which may cause calcium deficiency. Therefore, even after giving birth, mothers should pay attention to take calcium tablets to supplement calcium, need to be under the guidance of the doctor. Mothers who have back pain after giving birth, which is not relieved after resting, taking calcium supplements and keeping warm, as well as adjusting the breastfeeding position, or is accompanied by other symptoms, need to go to the hospital in time for checkups and treatments, and carry out standardized treatments.