Back pain in pregnancy may be caused by uterine compression, lumbar and dorsal myofasciitis, calcium deficiency and so on. 1. Uterine compression: mostly seen after the middle of pregnancy. As the uterus rapidly increases in size, it will compress the nerves in the pelvic and abdominal cavities, and may also compress the nerves that innervate the back, making the nerves tense, which will cause back pain in pregnant women. 2. Lumbar back myofasciitis: when pregnant, position changes are not as free as when not pregnant, prolonged sitting and standing will cause spasm of the lumbar back muscles, resulting in inflammation of the back fasciitis and muscle tissues, which will stimulate the nerves of the back, and therefore back pain. At the same time, it may be accompanied by limited activities. 3. Calcium deficiency: in the middle and late stages of pregnancy, the fetus grows faster, the demand for calcium will increase, if the pregnant woman in the pregnancy of insufficient supplementation, it is easy to cause thoracolumbar spine joint pain, will also involve the back muscles cause pain. It is recommended to take more rest during pregnancy. If the above symptoms do not improve in a short period of time, please go to the hospital immediately.